On large trash pulls on DRK, DA DP and DA DD render you nearly invulnerable. Dark Mind trivializes pulls with harder hitting caster mobs like sprites which the other two tanks can sometimes struggle with (remember the Security Command room in Stone Vigil?) During the time in between, the self healing from Abyssal Drain while Blood Price is up is amazing.

You have more AoE moves at your disposal than any other tank, two of which are oGCD, and the other two of which are better than their counterparts on other tanks. Unleash is better than Flash. Abyssal Drain is more versatile than Overpower.

For speed-running, you can sprint between mob sets and primarily use MP moves to hold aggro and dps while your TP recovers. And then there's Plunge. Glorious Plunge.

All three tanks are capable of doing the more challenging content in this game effectively, and each has their strengths and weaknesses. But dungeons and AoE tanking? No tank does it better than DRK. You can't stick to using a few skills and expect to get by, though. You need to make use of your entire toolkit and plan your MP usage in advance.