Why I love Dark Knight...

[Fluffernuff]

DRK is pretty well balanced right now if you ask me. I'd even say on the slightly weaker side of the raid tanking scales. It very hardly depends on your healers' abilities to DPS, and the fight you're going into.

4/5ths of the new content has physical heavy-hitting attacks, so DRK can find themselves on the weaker side of the defensive spectrum for this tier, which can mean less healer DPS. They bring more personal DPS to the table and also Reprisal, but PLD's capability to tank physical stuff and the fact that Rage of Halone reduces Str and can have 100% uptime (which would be a DPS loss for the Paladin but perhaps a DPS gain for the healers) make DRK, imho, the weakest of the three tanks for the current raid tier, though not in a level where it has too much impact on the meta anyways.

I personally prefer healing PLDs, but I don't care if it's a DRK instead.

Indeed! I would agree on a boss encounter with 1 enemy (Raids), DRK falls just a tad bit shorter of the 2. Not so much HARDER to heal, but just lurking around the tanking forums, it seems that DRK just doesnt have enough effective tools in a longer 1 enemy fight to keep up with the tankbusters... or rather they simply have too many longer cooldowns. but I do agree, all 3 tanks are totally interchangeable, and it's amazing.
My last sentence was more of a snark than anything. If DRK is so hopelessly squishy, then why would ANYONE want it taking all the hits? Obviously, no one would and DRK wouldnt be MT over a PLD... IF this were the case.

oh jeez, LD.... I forgot that existed because it just never comes up for me... Apparently it has it's uses in savage as an extra cooldown, but it's downside is just so anti-tank it boggles my mind... It just has that much more added coordination/communication that the other 2 "oh sh!t" buttons WAR and PLD don't have... Its like a "worse" Holmgang with a longer CD and a HG that kills you on a shorter CD. Holmgang CAN get you killed, sure, but it wasn't the effect of holmgang that killed you.
not to mention that LD actually becomes WORSE the better gear DRK has- it makes that healing requirement HARDER to heal outside of a WHM benediction. it'd rather silly. clearly not USELESS, but still...so, so silly.