DRK's AoE output is alot more than you are thinking. Flood of Shadows is *really,* *really* strong as a 250/300 **oGCD** AoE attack. Without their respective burst windows in IR, FoF, NM, the other tanks have virtually no comparable oGCD and need to catch up through more than *8* GCDs to reach that initial 750/900 pot burst from just Flood alone. Throw Abyssal Drain (200) and Salted Earth(360) in and you will understand why DRKs AoE GCDs are comparatively lower with Stalwart Soul being only a 10 pot upgrade from Unleash and Quietus only 70 pot higher.

Throw in the mana and blood gain from Stalwart and Blood Weapon and DRKs Flood uses per pack rises from 3/4 to 6-7. That's another 600/900 oGCD pot thrown ontop.

The nerf to Abyssal Drain and subsequently Steel Cyclone for Warrior is specifically to kneecap both DRK and WAR from being overpowered dungeon god tanks to being balanced with PLD and GNB. It was fun to recover ourselves and pull those 1v1 clutch moments with bosses when the party was dead but it was broken. SE clearly doesn't want us to refill our HP to 100% per GCD whilst PLD and GNB have no such options. It is not completely taken away as Abyssal Drain albeit being a cooldown still heals per target and can be used as a burst heal in large packs and Warrior gained Nascent Flash where they have to actively manage their bursts into it whilst have a reasonable 25 second cooldown on the skill to prevent the aforementioned broken self sustain.

The defensive gap in their kit only really exists in Dark Mind where WAR has Thrill and GNB Camouflage. But with current tank toolsets adding Arms Length and the new Reprisal, we have more than enough cooldowns to handle any situation, provided the DPS aren't single targeting a massive pull.

As the tank with the strongest AoE Burst at 80(Living Shadow, 4-7 Flood, Abyssal Drain, Salted Earth) and the ability to "cooldown" their burst AoE engine(Flood) faster by regaining mana in between pulls DRK is in a very good state.

In Savage raids/trial DRK is one of the most durable tanks next to WAR whilst having second last/last damage output on average(remember this margin is less than 3%. We're looking at 300 DPS at most currently and your own personal skill is what matters more) and gaining the most from raid buffs thanks to their incredible flexibility which would put them 2nd highest when optimized.

DRK is fine. It's skill acquisition during leveling is a big think with TBN at 70 but everything else is designed and relatively balanced reasonably.