This guide is from my personal experience, as Deathknight, of not having the luxury of farming for drops in normal instances. I wrote this guide with the focus on quest rewards, reputation vendor options and crafted items, making it possible for a casual player to plan & acquire these rewards without worrying about 'random drops'. I also included basic information to
WoWhead.com to get you started. Paladin and Warrior tanks will find most of this guide useful, for the focus on 'easily' acquired items.
The order is based primarily on the best defense item. I do try to point out items that make the list, but aren't worthwhile in acquiring. Usually, another item exists that is both superior and easier to acquire. Most items have required levels between 75-78, making them possible to acquire prior to level 80. I also list other items that can be collected in the same quest chains, so a players looking up a specific slot will find related quest items. While I do list items rewarded from quest chains in dungeons, the rewards are assured if you can clear the instance. I found that 'drop rate' superiour to any bosses' loot table

.
Please post errors, especially in quest chains or links so I may correct them. Also, as an alliance player, I have not done horde versions of quests, so I based my ranking/notes on my alliance experience and wowhead information.
Enchantments
The only two enchantments a tank 'must have' for heroics are
Enchant Chest - Greater Defense (+22 Defense Rating) &
Enchant Cloak - Titanweave (+16 Defense Rating). The reasoning is these enchants are relatively easy to acquire and will go on gear that won't be replaced quickly.
The Honored - Hrodir enchant
Lesser Inscription of the Pinnacle (+10 Defense Rating & 15 Dodge Rating) &
Arcanum of the Stalwart Protector (20 Defense Rating & 37 Stamina) require notable reputation and gold investments, but are desirable.
Reputation
The general consesus of grinding Wyrmrest to Revered is accurate, as it gives the most defense on gear for the effort. You can substitue other items, however, to avoid endless dailies or instances. At the very least, get to Honored, as there is nothing superior to
Cloak of Peaceful Resolutions pre-heroic/raid. After you get to Wyrmrest Honored/Revered you start grinding Argent Crusade rep for
Arcanum of the Stalwart Protector (20 Defense Rating & 37 Stamina) and possibly (at Argent Crusade - Honored) the
Special Issue Legplates.
Weapon
Suggested DK runeforge:
Rune of the Stoneskin Gargoyle Axe of Bloodstained Ice
That's it. The only 2H with defense.
Alliance Chain
Start with
It's All Fun and Games chain going to
Exploiting an Opening's chain leading to
Do Your Worst.
Horde
Start with
It's All Fun and Games chain going to
Opportunity's chain and end in the chain
Do Your Worst.
Note you need to complete the Argent Crusade quests to open up
It's All Fun and Games. Thankfully, the helm
The Crusader's Resolution comes from those chains' ending in Crusader's Pinnacle.
Helm The Crusader's Resolution
Lots of prequisite Argent Crusade quests to reach this helm in Icecrown. You'll get this if you work to acquire the
Axe of Bloodstained Ice.
Greathelm of the Titan Protectorate
Mid level helm for gearing. Chain starts with
The Lifewarden's Wrath.
Tempered Saronite Helm
Crafted from 12 Saronite Bars (24 ore) plus 1 Eternal Earth.
Neck Betrayer's Choker
Reward from long quest chain in Zul'drak, started by killing Withered Trolls for an
Unliving Choker. You can pick up this drop during normal questing. Also, the socket can be slotted with +defense or +defense/stamina gems such as a
Thick Sun Crystal.
Chain of the Sovereign
Acquired in process of opening Ebon Hold.
Alliance -
Woven Steel Necklace
Horde -
Tiled-Stone Pendant
Slightly different 'low level' rewards from Utgard Keep for each faction, using the same quest.
Shoulders Pauldrons of Reconnaissance
Save Bran. Get this. Profit.
Tempered Saronite Shoulders
Crafted from 12 Saronite Bars (24 ore).
Tundra Pauldrons
Tank-starter reward, likely something you pick up as you level in Northrend. You can also get
Gauntlets of the Disturbed Giant &
Boots of the Unbowed Protector in the
same run.
Chest
Suggested enchant
Enchant Chest - Greater Defense (+22 Defense Rating)
Breastplate of the Solemn Council
Rep - Revered - Wyrmrest. Amazing Chestpiece.
Silver-Plated Battlechest
Quest from the start of Utgarde Pinnacle.
Ivory-Reinforced Chestguard
Rep - Honored - The Kalu'ak. You can hit honored easily in questing. This item is a 'junior' version of
Breastplate of the Solemn Council.
Cloak
Suggested enchant
Enchant Cloak - Titanweave (+16 Defense Rating)
Cloak of Peaceful Resolutions
Rep - Honored - Wyrmrest. Get it.
Cloak of Tormented Skies
Crafted from 6 Heavy Borean Leather, 5 Eternal Airs and 5 Crystallized Water.
Bloodbane's Resolve
Long series of quests for a mediocre upgrade to above cloaks. Notable for it being a quest reward.
Wrist Bracers of Reverence
Req Lvl 77 for quest. Chain requires multiple Occulus runs, but you pick up
Staunch Signet in a preceding step.
Tempered Saronite Bracers
Crafted from 13 Saronite Bars (26 ore).
Cobalt Bracers
Slightly inferior to
Tempered Saronite Bracers but only requires 4 Cobalt Bars (8 ore).
Hands Daunting Handguards
Amazing gloves. Crafted from 12 Saronite Bars (24 ore) plus 1 Eternal Earth. Slightly superiour to
Tempered Saronite Gauntlets for similar materials.
Gauntlets of the Disturbed Giant
One prequistie step, then a Nexus run. Note you can get
Tundra Pauldrons &
Boots of the Unbowed Protector in the
same run.
Expelling Gauntlets
Easy quest in Azjol-Nerub, only requiring you kill the first boss to complete.
Belt
Crappy Itemization. No other way to phrase it.
Tempered Saronite Belt
Crafted from 6 Cobalt Bars & 5 Saronite Bards (12 & 10 ore, respectively).
Cobalt Belt
Crafted from 4 Cobalt Bars (8 ore).
Gutbuster of Aldur'thar
Mentioned for completeness. Requires flying to reach the quest giver, with additional prequisite quests.
Pants Daunting Legplates
Crafted from 14 Saronite Bars (28 ore) plus 1 Eternal Earth. Amazing pants.
Special Issue Legplates
Rep - Honored - Argent Crusade. The socket with a defense gem can almost match Daunting Legplates, but the hit rating is great as well.
The quest rewards
Iron Colossus Legplates &
Leggings of Forceful Purification both require long chains for minor increases. If you quest in Grizzly Hills, these may be worth acquiring as you level.
Boots Sabatons of Draconic Vigor
Rep - Revered - Wyrmrest. Solid boots with hit rating.
Tempered Saronite Boots
Crafted from 3 Cobalt Bars & 8 Saronite Bars (6 & 16 ore, respectively).
Boots of the Unbowed Protector
Another starter piece of gear with one prerequisite quest, but you can get
Gauntlets of the Disturbed Giant &
Tundra Pauldrons in the
same Nexus run.
Rings Staunch Signet
Req Lvl 77 for quest. Continuing the chain (multiple Occulus runs), you can also get
Bracers of Reverence.
Solid Platinum Band
Simple quest in Gun'drak for identical ring to Staunch Signet.
Kurzel's Warband
One prerequisite quest to this Drak'Tharon reward.
Stoneguard Band
Crafted from 2x Eternal Earths, ideal for a +stamina gem for socket bonus. Equip-Unique, so you can only use one.
Trinkets Dabiri's Enigma
While this quest can be solo'ed near/at 80 (tip - kill the adds when they spawn), it's better to bring a friend or two.
Regal Protectorate from the quests:
Horde -
Cruel's Intentions
Alliance -
Overlord
In summary, if you collect, craft or otherwise acquire the lowest defense item in each category, you'll be at 485 defense rating, needing another 204 to hit the ideal 540 Defense Skill. Additional gear, enchants and/or gems are needed to fill that void.
Deathknights using the
Rune of the Stoneskin Gargoyle will net you the equivalent of about 123 defense rating, leaving 81 rating to fill by improving gear, enchants and gems. Note that the suggested enchants (
Enchant Chest - Greater Defense (+22 Defense Rating) &
Enchant Cloak - Titanweave (+16 Defense Rating)) cover most of that rating gap.