I think it is worthwhile to discuss and educate the community about the capabilities and skill sets of each tank class/spec. That said your method is cursory, subjective, and very much reductionist.
So, rather than starting with what you think each tank is good at while admitting you don't know more than half the options well at all, why don't we compile how each class works and what tools they have?
There are 6 tank class/specs, mind you, suitable for heavy end-game tanking:
Bear-oriented Feral Druid
Blood Death Knight
Frost Death Knight
Unholy Death Knight
I make a point to separate the DK specs because each one operates very differently, has it's own strengths and weakness, and even it's own tanking tools and CDs.
If you want to compare important tanking factors there are many items and some of the class specs work in particularly unique ways. Here's a very brief summary in terms of survival:
Warriors = Plate armor and shields, can dodge/parry/block. Warriors get 10% dmg reduction just from being in defensive stance. They can get 10% more armor from gear, 5% dodge, 5% parry, and 5% block directly from talents, along with +30% block value. They have a 30% chance to crit-block for double their normal block value. They get +6% to Strength, +6% to Stamina, and 6 expertise from talents. Against magic they get 6% spell dmg reduction and can get improved Spell Deflection (normal version can reflect a single spell cast on 10 sec CD, improved it can reflect from the four closest party members and reduces your chance to be hit with spells by 4%). Warriors get a few different CDs.
Shield Block = 100% block chance for 10 sec, with double the base block value, on a 1 min CD, talentable down to 40 sec CD.
Shield Wall = 60% less damage taken for 12 sec on 5 min CD. Talents can reduce this to 4 min CD (glyph commonly used can reduce the CD by 2 min more but reduces it to 40% dmg reduction).
Last Stand = talented this increases the warrior's health by 30% for 20 sec on a 3 min CD. Glyphed it is only a 2 min CD.
Additional special skills, warriors can intervene a target which will reduce their threat by 10% and take the next melee/ranged attack instead of the target on a 30 sec CD. Warrior's method of applying the de-hasting melee debuff to targets is improved Tclap which hits unlimited targets in a 10 yrd range (*fact check please*). Warriors can provide AP reducing shout (as can Lock's curse, Hunter pet special, and Bears) and health increasing shout (as can Lock demon and dps warriors).
Paladins = Plate armor and shields, can dodge/block/parry. Paladins rely on Righteous Fury for threat buffing, which talented reduces all damage taken by 6%. They get 3% additional reduction in all damage taken by another talent, and when their health is below 35% health they take 30% less damage from everything on top of those. They get 6% less spell damage taken from a separate talent, this represents the only specific anti-magic ability. They get +15% strength, +14% stamina, and 6 expertise from talents. They also receive the standard 5% dodge and parry, +30% block value, and +10% armor from gear. From talents they have a 10% chance on being hit to increase their chance to block by 30% for 10 sec or 5 blocks, and can increase all healing effects on themselves by 5%. For CDs:
Holy Shield = +30% chance to block for 10 sec or 8 blocks on 8 sec CD.
Divine Plea = with one of the fancy new glyphs this not-survival move becomes an additional survival factor reducing all damage by 3%. Combined with Guarded By the Light, this can be up 100% of the time in any single fight.
Divine Protection = 50% all damage reduction for 12 sec, 3 min CD. With prot talents it is reduced to a 2 min CD.
Lay on Hands = gives a target (tank possibly) an amount of health equal to the pallies' max health (for the tank restores them to full health, can crit >.>) and a chunk of mana. 20 min CD can be talented down to 16 min which also makes it buff the targets armor by 25% for 15 sec, and can be glyphed to trim 5 more minutes off the CD to a minimum of 11 min CD fully buffed.
Pallies can Hand of Protection to make a target immune to physical damage for 10 seconds on a 5 min CD. They can Hand of Salvation to reduce friendlies' threat on a 2 min CD. They can also hand of Sacrifice to take 30% of the damage for the target until it's transferred the tank's full health. A prot tank's aura's increase healing effects on everyone affected by 6%, though this is exclusive with Resto druid's tree aura. Pallies can increase party/raid members' fire, frost, or shadow resists by 130, or armor by 1200 (1800 with prot talents), though these can be offered by any pally in the raid. Prot pallies can provide Blessing of Sanctuary which reduces all damage taken by 3%, though that buff can be provided to other tanks in the same raid with a prot pally and it does not stack with a warrior's vigilance or a Disc Priest's Renewed Hope. Judgement and Seal of Light can restore health to the tank, though this too can be provided by other pallies in the raid. Pally's melee de-hasting ability is applied with their judgment so it is functionally single target only.
Druid = Druids wear leather gear and get a big armor buff from being a bear (370%, fully talented it is 588%). Druids cannot parry or block, only dodge. In addition to the armor buff, bear form increases the druid's stamina by 25%. Talents give the bear +10% armor from gear, +10 Expertise, +10% dodge, +16% stamina, +6% Strength, +6% Agility, and 6% reduced chance to be crit. Bears get an ability called Savage Defense which is essentially a shield block type ability. When they crit they get a damage shield equal to 25% of their AP (functionally block chance = crit chance and block value = 25% of AP). This works out a bit different than block since it does not feature in the hit table, instead it is simply saved for the next hit (block is only possible if the strike isn't a miss/dodge/parry, but if you DO dodge, it doesn't store up that block that could've been for the next swing), bears do not have talents to buff this ability like warriors and pallies can buff their shield block ability. Bear CDs are as follows:
Barkskin = Bear's answer to the other class's protection abilities, this reduces all dmg taken by 20% for 12 sec, on a 1 min CD.
Frenzied Rejeneration = the bear converts up to 10 rage per second into health at a rate of 0.3% total health per point. Lasts 10 sec on a 3 min CD. Glyphed this also increases all healing effects on the druid by 20%. Note, this ability consumes rage so it is at the expense of dmg threat.
Survival Instincts = +30% health for 20 seconds on a 3 min CD. Glyphed this becomes +45% health.
Bears have Leader of the Pack that will allow them to regen 4% of their max health every time they crit, but this is graned raid wide by any feral druid in the party/raid. Bears provide the AP reducing ability that warriors do. The bear de-hasting debuff is applied by maul and mangle, so it is on restricted numbers of targets. Since you can only hit 1-3 targets at a time and requires two hits to stack it and one to maintain after that, it is not easy to maintain it on pulls with many targets.
Death Knights (general) = DKs wear plate armor with no shield. They can dodge and parry, but not block. All DKs normally will take +15% armor from gear, +5% dodge, and 5% all dmg reduction that will be functionally up 95-100% of the time (requires both Blood runes on CD once every 10 sec). Specific additional details depend on tree. Frost Presence increases the DK's armor by 80% and health by 10%. DK's get 25% of their Strength as parry rating which buffs their parry chance by a noticeable amount (~4-7% depending on gear at 80). All DKs share 2 main survival CDs:
Icebound Fortitude = 20% dmg reduction buffed by defense (~35% at 540 def) for 12 sec on a 1 min CD.
Anti-magic Shell = reduces all magic damage by 75% for 5 sec or until it absorbs 50% of the DK's total health.
Death Knights' melee de-hasting ability is applied with Frost Fever which is easily maintained on all targets in range and lasts 15-21 sec per application depending on talents.
Blood = from the blood tree you can get +8% Strength, +6% Stamina, and +6 expertise. Also one talent will give the DK a chance equal to his parry chance to take 45% less damage from direct damage spells (as opposed to periodic spell dmg). Another reduces the damage of any hit that takes the tank below 35% health by 15% on a 15 sec hidden CD (only procs on hits larger than 5% of total health). Otherwise Blood relies heavily on self-healing to offset damage. 3 CDs, 0-2 passive effects, and one common ability are used for this. The CDs are:
Vampiric Blood = increases the DK's total health by 15% and increases all healing effects on him by 35% for 20 sec (30 sec with glyph). 2 min CD.
Mark of Blood = for 20 seconds or 20 hits, the enemy target affected heals who they damage for 4% of their total health. This heal triggers immediately after the damage like Earth Shield and Prayer of Mending so it won't overheal unless the hit is smaller than 4% and can be used to support other tanks and raid healing.
Rune Tap = restores 10% of the tanks total health on a 1 min CD. Talented this becomes 13/16/20% of total health on a 50/40/30 sec CD (glyphed 22% on the tank and 10% to everyone else in the party).
DK's have Death Strike which restores 5% of their health per disease on the target which will heal for 50% more (next patch) for a Blood DK. Two less common talents allow the DK to regenerate 4% of his damage done as health while tanking, and another can proc Blood Worms to heal the tank for small amounts as they do damage.
Frost = from the Frost tree you can get +3% miss, +2% all dmg reduction, and 5 expertise. A special talent allows you a 30% chance when taking magic damage to get 50 resistance to that school of magic for 18 seconds, and that can stack up to 3 times and multiple types can be applied at the same time on individual timers (i.e. fire, frost, nature, arcane, etc). Frost buffs the duration of Icebound Fortitude up to 18 seconds, and has one CD only that it adds to the mix:
Unbreakable Armor = all damage taken is reduced by a value equal to 5% of the DK's armor (~1k-1.6k depending on gear, glyph increases that value by 20%) for 20 sec on a 2 min CD.
Frost DK's have access to Death Strike though it receives no buffing from Frost and is not the preferred threat tool for the cost.
Unholy = from the Unholy tree, you can get 6% magic damage reduction, buffs AMS to reduce magic damage by 100%, and adds 2 CDs to improve survival:
Anti-Magic Zone = this zone absorbs 75% of magic damage taken by all inside for 10 seconds up to a maximum buffed by AP (14-20k total dmg but will reduce the full 75% on every target from a single burst even if it surpasses the total allowance).
Bone Shield = this applies 4 charges (6 glyphed). So long as at least one charge remains the DK takes 20% less damage from everything. Each time the DK takes damage a charge is consumed, though charges have a hidden CD (~2 sec). Shield lasts 5 min otherwise and has a 2 min CD.
Let's look at some passive buffed highlights:
Warriors = +6% Str, +6 Expertise, +6% Stam, +10% armor from gear, +5% dodge, +5% parry, +5% block, +30% block value. 10% all dmg reduction, 6% spell dmge reduction. 30% chance for double value block.
Pallies = +15% Str, +6 Expertise, +14% Stam, +10% armor from gear, +5% dodge, +5% parry, +30% block value. 9% all dmg reduction, 6% spell dmg reduction, 10% chance per hit to get +30% block chance for 10 sec. +5% heals on self.
Bears = -6% chance to be crit, +6% Str, +6% Agi, +10 Expertise, +25/16% Stam (+45% combined), +10% armor from gear, +588% armor from gear, +10% dodge. Crits create a damage shield equal to 25% of the bear's AP to act as a physical damage shield.
Blood DKs = +6% Str, +6 Exp, +6% Stam, +10% health, +15% armor from gear, +80% armor from gear, +5% dodge, 25% of Str as Parry rating. 5% all damage reduction with an additional maintained 5% all damage reduction. Chance equal to parry chance to reduce direct spell damage by 45%. Hits that take you below 35% are reduced by 15% on a 15 sec CD. Self-heals can be substantial and 'passive'.
Frost DKs = +5 Exp, +10% health, +15% armor from gear, +80% armor from gear, +3% miss, +5% dodge. 7% all damage reduction, with an addition 5% damage reduction maintained. 30% chance on spell dmg taken to stack 50 resistance to that school for 18 sec, can stack up to 3 times.
Unholy DKs = +5 Exp, +10% health, +15% armor from gear, +80% armor from gear, +5% dodge. 5% all damage reduction, with an addition 5% damage reduction maintained, 6% magic reduction.
Beyond the passives, all the class/specs get a big dmg reducer:
Warriors = 60% dmg reduced for 12 sec, 5 min CD (talented -1 min to CD, glyphed becomes 40% dmg reduction and -2 min to CD)
Pallies = 50% dmg reduced for 12 sec, 2 min CD.
Blood/Unholy DK = 35% (+/- with def) dmg reduced for 12 sec, 1 min CD.
Frost DK = 35% (+/- with def) dmg reduced for 18 sec, 1 min CD.
Bear = 20% dmg reduced for 12 sec, 1 min CD (glyph affects pvp only reducing chance to be crit further while it's up)
Warriors and Pallies get very short CD abilities that buff their survival well:
Warriors get guaranteed big blocks for 10 sec every 40, 25% uptime used on CD.
Pallies get much 30% higher block chance and blocks do reflective damage, 100% uptime on a single target, more targets reduce the uptime.
Bears, Warriors, and Blood DKs get a big activatable health buff. Bears' is +45% for 20 sec every 3 min. Warriors' is 30% for 20 sec every 3(2) min. Blood DKs' is +15% health for 20(30) sec every 2 min and comes with a +35% all healing buff.
Now, using 8.5 tanking gear sets (only gear not trinkets, rings, necks, or weapons) to get an idea about how passive multipliers break down for mitigation and health:
Armor = 2400 * 1.10 * 6.25 = 16503 (+482 agi = +964 armor)
Stam = 530 * 1.16 * 1.25 = 769 = 7505 health
*7 non-meta sockets (3/2/2 RYB)
Armor = 9538 *1.10 = 10492
Stam = 671 * 1.06 = 711 = 6934 health
*7 non-meta sockets (0/3/4)
Armor = 9538 *1.10 = 10492
Stam = 671 * 1.14 = 765 = 7469 health
*7 non-meta sockets (4/2/1)
Armor = 9538 * 1.15 * 1.80 = 19744 (note: DKs cannot get shields)
Blood Stam = 697 * 1.06 = 739 = 7208 health *1.10 = 7929 health
Frost/Unholy Stam = 697 = 6790 health *1.10 = 7469 health
*7 non-meta sockets (2/1/4)
Shields at this level are just shy of 8k armor, so bears actually end up slightly the lowest for armor from gear even though they will have much more agility and therefore armor than the plate wearers will, and will likely be able to get more armor buffing on itemization since they don't need defense and they get a lot of value from Agi which will be distinctly better buffed for them in raids. DK's bonuses put them slightly ahead of the others in total armor value thanks to the multipliers, though they do not have a block-type mitigation effect like the other 3 tank classes.
Warriors get the least straight health from stamina, but they also rely on it the least in their survival mechanics. Pallies, Bears, and Frost/Unholy DKs have about the same from core pieces, but again, Bears will likely pick up more from additional pieces since their multipliers are significantly larger than the other classes. Pallies gravitate towards stamina because it works well with Ardent Defender and Touched by the Light (30% of Stam = Spellpower for a big threat buff), so they will likely pick up stamina items the same way, but they won't get quite as much mileage as bears will. Blood DKs get the most from core gear by a small margin, and will get ever so slightly higher value for stam stacking than Pallies, though Bears multipliers will still out-pace them by a decent margin. Blood DKs of all the class/specs arguably get the most out of stam stacking since they have 4 self-healing abilities they rely on to functionally mitigate damage that scale on total health, and Blood DK's are unique in the tanking kingdom for that reliance on self-heals. I haven't mentioned it previously, but DKs can also use Rune of Stoneskin Gargoyle which will increase their stam by another 2%.
Avoidance is hard to put a finger on as it diminishes and there are a variety of different non-set pieces that vary in value greatly for what they buff. Let me see what I can pull from core gear values, as we can say that anyone could get the other non-set pieces regardless of class/spec (though again, different classes value stats differently). I'll include Block % on this list, though they aren't avoidance they're easier to track here. Also, still speaking passively not factoring CDs.
Def Rating = 0
Dodge Rating = 0
Agi = 455 (note: druid weapons will likely also have high Agi values)
*damage shield is based on crit and AP for frequency and intensity respectively
Def Rating = 257
Dodge Rating = 217
Parry Rating = 60
Block Rating = 51 = 3.11%
Block Value = 166 + (443 Str / 2) = 388
*+5% dodge, +5% parry, +5% block
*30% chance block value will double on block
Def Rating = 268
Dodge Rating = 153
Parry Rating = 147
Block Rating = 80 = 4.88%
Block Value = 136 + (491 Str / 2) = 382
*+5% dodge, +5% parry
*10% chance on hit to +30% block
Def Rating = 294
Dodge Rating = 165
Parry Rating = 227 + (390 Str * 0.25) = 325
*all DKs = +5% dodge
*Frost +3% miss
*all DKs have access to personal runes that add avoidance/Def skill but don't effect the diminishing returns, this is +4% parry or +25 def skill (=1% miss, 1% dodge, 1% parry) with +2% stam.
Obviously the formulae are all rather messy and depend on what non-set pieces you are using so you know how diminishing returns break down. At a glimpse though we can tell that Warriors have about 30% more dodge on their core pieces, DK's will have 5 times the warrior's and over double the pally's parry rating, and the DK will have the most dodge/parry buffing from Def. DK's get the least % from talents but will get a nice buff from their rune (almost making up for that). Bears will rely very heavily on their Agility, though they match the Warriors and Pallies for raw avoidance from talents. In the wash, and based on conversations with tanks of other classes, I'd expect the avoidance values to go roughly in this order for similar gearing and gem/chant focus:
DK > Bear > Warrior/Paladin
Though I also expect the spread from highest to lowest to only be on the order of 4-8% at most.
The last comparison I'll touch on today is cooldowns. Each class/spec has their own unique tools to use through adversity. Again we'll disregard trinkets since these could/should be universally attainable and different classes will like different trinkets for their own reasons.
Obviously, Bears have the least survival CDs, most of their CDs are threat focused. Barkskin is the smallest of the protection abilities, but it is on a fast timer like DKs. Survival Instincts gives them a significant health jump, and bears are already primed to have the largest health pools by a margin. Bears get the ability to regenerate a reasonably large amount of their health on a moderately long CD. Frenzied Regen is worth 3% max health, per second, for a total of 30% max health over 10 seconds in the best case. Glyphed this value alone increases to 36% plus it buffs other incoming heals. The 3 min CD leaves this as more of a once or twice per big epic boss fight. Bears are for all intents and purposes, designed to have a higher survival baseline before CDs.
Paladins also sport a pretty small number of CDs but they are very potent. Their protection skill, Divine Protection, is solid at 50% and a 2 min CD, and glyphed they can take a voluntary hit to their own threat to get another 20% damage reduction for 10 sec on a 2 min CD with Hand of Salvation, though this has it's own risks of course. Holy Shield as an always up ability is very powerful against one or two targets as it is functionally up 100%. Against very large pulls it won't last quite as long though it is not an extreme reduction. Like Shield Block for Warriors this value increases noticeably against faster swings with smaller individual hits. Lay on Hands is about as collosal a save as you can get, but it is the only remaining 'tank' ability on such a long CD. It's amazing the moment you need it, but it can't be used casually.
Warriors have versatile CDs that can suit a variety of needs. The Warrior protection CD, Shield Wall, is the biggest among the tanks, even though glyphed it matches Pallies, unglyphed it is a HUGE value but only usable half as often. Shield Block has a reasonably high coverage at 25% for ensuring that anything not avoided is blocked, making warriors pretty regularly capable of taking less physical damage particularly through fast swinging bosses or lots of small hits. Spell Reflection is a powerful ability in certain situations even if the target is immune to the effect being reflected.
DK's originally were the CD tanking class. Smart rotation of CDs for coverage was essential as they would otherwise take noticeably more damage than any other tank. Things have changed and times have shifted. DK's still have very useful CDs but they are far less essential. IBF rings in as the most pivotal core ability. Compared to the equivolant talents for Pallies and Warriors it is very powerful thanks to its 1 min CD, but you'll find looking over the values that this is to make up for the wealth of other survival tools that the other classes have, which is most notably the ability to block. Each tree has its own system of CDs that it relies on. Frost is by far the least CD dependent, though it sports a longer duration IBF and Unbreakable Armor it will take less damage without cooldowns. Unholy relies entirely on Bone Shield for the bulk of the mitigation work, and while it works well in good gear it requires a fair amount of attentiveness to get the full value. So long as it is up Unholy is remarkably durable, and it is fantastic against large count pulls and multiple damage sources that come simultaneously. Blood, as I mentioned, is unique among the tanks as it uses self-heals to off-set damage taken. Used to their fullest these heals can actually put the Blood tank at a higher effective mitigation level than the other two specs, but that hinges heavily on the degree of the damage being taken, the skill of the tank timing the heals well, and frequent use of the additional heals. Vampiric Blood may be the single most powerful CD available in 25-man raids, as a Blood tank with a significant health pool will be able to be healed through just about anything for 30 sec.
Threat is a completely different matter, and I'll respond tomorrow with more on that, probably.
I don't think any of the classes stands noticeably above the others, they each have their own strengths and weaknesses that match well or poorly with the different challenges available. No tank is incapable of tanking some particular scenario, and no tank is TOO good at tanking something particular, Blizz has seen to that.