I made this small chart to allow comparing of the different points for each class ON PVP:

DK
- Sustained DPS: High. Mostly physical if blood. Unmitigated otherwise.
- Burst DPS: High. Same as above.
- CC: High as Frost (Dispellable, 1 min cd). Low with ghoul stun as Unholy.
- Physical Survival: High in all specs.
- Magical Survival: High if unholy. Normal otherwise
- Snare: Physical snare (both 50%) if blood or unholy. Magical snare, COI, without talents, which is VERY good against teams without dispel, and just good with dispel.
- Ability to kite melee: High.
- Time on target: High.
- Unsupported mobility: Normal. - Supported Mobility: High
- Healing debuff (As requested by Nex-Moonglade): None

Druid:
- Sustained DPS: High in both balance and feral. High sustained healing as resto.
- Burst DPS: High as feral (though it is one of the hardest burst to prepare since it requires quite some timing on buffs/debuffs). High as balance if there's no LoS problem.
- CC: Very high against melee if balance or restoration. Normal against ranged. If feral, very high against everyone, but limited to shifting.
- Physical Survival: High on both feral and restoration. Low if moonkin.
- Magical Survival: High if restoration. Low otherwise.
- Snare: Physical snare (50%) if feral.
- Ability to kite melee: High.
- Time on target: High if feral. Normal otherwise.
- Unsupported mobility: High. - Supported Mobility: Very High
- Healing debuff: None

Hunter:
- Sustained DPS: High if survival, normal otherwise.
- Burst DPS: High unmitigated if survival. High physical otherwise.
- CC: High dispellable if survival. Normal dispellable otherwise.
- Physical Survival: Normal. They survive because they can kite melee really well.
- Magical Survival: Low.
- Snare: High (undispellable).
- Ability to kite melee: Very high, snare traps, snare shots, wingclip, disengage.
- Time on target: High.
- Unsupported mobility: Normal. If snared they have problems with targets using columns. - Supported Mobility: Normal, High depending on each situation.
- Healing debuff: 50%, instant cast, undispellable.

Mage:
- Sustained DPS: High if they can get some casts.
- Burst DPS: High if arcane. High if frost on shatters (which are quite common).
- CC: Very high against melee. High otherwise. Dispellable.
- Physical Survival: High if frost. Low otherwise.
- Magical Survival: Very high if they have the Mage Armor buff and are arcane or frost.
- Snare: High, all dispellable.
- Ability to kite melee: Very high as frost.
- Time on target: High.
- Unsupported and Supported mobility: High.
- Healing debuff: None

Paladin:
- Sustained DPS: Normal if retribution. Low otherwise.
- Burst DPS: Very high if retribution since it's unmitigated and holy has no resistances.
- CC: Low if protection / holy. Normal otherwise. Dispellable.
- Physical Survival: High if holy / prot. Normal otherwise.
- Magical Survival: Normal.
- Snare: None
- Ability to kite melee: High if there's no dispeller on the opposite team. Normal otherwise.
- Time on target: Normal.
- Unsupported: mobility: Normal/High. - Supported Mobility: High
- Healing debuff: None

Priest:
- Sustained DPS: High if shadow.
- Burst DPS: High if shadow.
- CC: Normal, dispellable. The category of CC (fear effect) is the one most effected by talents, racials, classes, etc.
- Physical Survival: Normal/high if discipline. Low otherwise.
- Magical Survival: High if healer since they can dispel diseases, magic, etc.
- Snare: None unless shadow, then it's dispellable and channeled.
- Ability to kite melee: Very low.
- Time on target: Normal.
- Unsupported mobility: Low. - Supported Mobility: Low / Normal
- Healing debuff: None

Rogue:
- Sustained DPS: High if combat, normal if assa, low otherwise.
- Burst DPS: High if assassination.
- CC: High, undispellable. They don't have spammable CC but can chain it for a long time if trinket is down with little ways to break it (freedom for stuns and berserker for sap/gouge).
- Physical Survival: Normal when they have their cooldowns. Very low after they are over.
- Magical Survival: High thanks mostly to the fact they shut down their enemies.
- Snare: High, supposedly dispellable but the proc rate on poisons makes it as if it were undispellable.
- Ability to kite melee: High if they have cds. Normal otherwise.
- Time on target: Very high if subtlety, high otherwise.
- Unsupported mobility: High if subtlety, normal/high otherwise. - Supported Mobility: High
- Healing debuff: 50%, dispellable, but poison proc so high it's almost always up.

Shaman:
- Sustained DPS: Low if restoration. Normal otherwise.
- Burst DPS: High if elemental or enhancement. Enhancement burst depends on both cds and rng (having procs at the same time as using stormstrike plus wolves for example).
- CC: Low. Normal against melee if elemental or enhancement. All dispellable.
- Physical Survival: High if restoration. Low otherwise.
- Magical Survival: High if restoration. Low otherwise.
- Snare: Dispellable snares or bound to totems.
- Ability to kite melee: Normal.
- Time on target: Normal.
- Unsupported and supported mobility: Normal.
- Healing debuff: None

Warlock:
- Sustained DPS: Very high if affliction and multiple targets (and not being utterly shut down by melee trains). Normal otherwise.
- Burst DPS: Very high if destruction and no LoS problems. Low otherwise.
- CC: Normal, dispellable. The category of CC (fear effect) is the one most effected by talents, racials, classes, etc.
- Physical Survival: Very low. They depend on their pet which can be killed by several melee classes in a matter of 3-4 seconds (at most). The demon armor gives them some physical survivability in exchange for some damage.
- Magical Survival: High if they are using a felhunter and are capable of self-dispelling, use shadow ward, etc.
- Snare: Weak dispellable snare if affliction (30%). If glyphed for it they have an undispellable? snare (70%), which CAN be dispelled if you dispel the dot of the shadowflame (intended?)
- Ability to kite melee: Very low. They have teleport on a 30 sec cd, which can be prevented if it's on LoS, or if a trap is put there, etc.
- Time on target: Very high.
- Unsupported mobility: Low. - Supported Mobility: Low/Normal
- Healing debuff: None except if affliction they get 30% against hots

Warrior:
- Sustained DPS: High if arms or fury.
- Burst DPS: Very high if arms against light armor. Normal otherwise.
- CC: Almost none. They have aoe fear on min cd. The category of CC (fear effect) is the one most effected by talents, racials, classes, etc. It's an incapacitate effect (breaks on first hit) on the target selected when you use it.
- Physical Survival: High if they drop their damage output by equipping a shield. Specially if they are prot.
- Magical Survival: Normal if they do the same as before. A bit higher if they are prot.
- Snare: Undispellable (50%) snare.
- Ability to kite melee: High.
- Time on target: High.
- Unsupported mobility: High. - Supported Mobility: High/Very High
- Healing debuff: 50% if Arms. 50% (2 debuffs) if Fury. Both undispellable. Edit: Arms also has the chance to get the debuff to 75% if they use a skill on a cast, also undispellable.

We all know there's a predominance of melee/healer in 2v2 and melee/melee/healer in 3v3. Why is that?

Well, the problem, as you can guess from the chart above isn't that ranged/casters need more armor, since you can see that most damage is unmitigated. However, ranged players need ways to avoid getting shut down, or ways to be able to escape.

The reasoning behind this is that melee are now mostly 100% of the time on their ranged target, except on the case of frost mages. Frost mages have the tools on which should be based new spells/abilities given to other ranged classes. One spec of a class currently has an aoe root on demand, snares attached to their main casted dps spell, aoe cone snare, aoe snare when focused (when shield blows), blink, iceblock, mana shield. That allows frost mages to be able to escape quite better than the other ranged.

Meanwhile, all melee have snares (except on ret paladin, but he has freedom and more running speed, but ok, here rets are at a disadvantage), and all of them are undispellable or almost impossible to dispel and not get applied almost instantly afterwards (read poisons). Only exception again is on a hybrid, the enhancement shaman.
Melee don't have pushback either (although this has been greatly improved since BC), but can cause it to ranged. They also have silences/interrupts and many gap closers.
Lastly the pet dependant classes are very different in nature:
DKs have ghouls that can be easily healed and easily resummoned (assuming unholy).
Hunters have pets with very different abilities.
Warlocks have a couple viable pets on arena.
What is the problem with pets? They are all VERY easily killed, but only DK pet can be resummoned easily any time. Warlocks have an easy summon just once every 15 minutes and they are the most dependant class on their pet. Once their pet is down twice, the pressure melee can deal on a warlock is incredible.
Original Thread: World of Warcraft (en) Forums -> Comparison Chart PVP(Update Corrections)