DRK requires very different cooldown usage from the other two tanks and that's why I think a lot of people are finding it squishy.

Basically the only two CDs you should be using for any reasonable amount of damage, by themselves, are Shadowskin and Shadow Wall. Everything else is something that should be stacked with something else. For example, in between Shadowskins and Shadow Walls, I mitigate damage with Dark Dance + 1 of Foresight/Awareness/Conva/Bloodbath.

Between DRK's surplus of cross class CDs and Dark Dance's brief 60s CD its good, consistent mitigation. And on that note, its worth saying that Foresight and Bloodbath scale in usefulness with your gear for defense and damage dealt/HP respectively, and particularly in Foresight's case, are only gonna become better and better CDs as ilvls rise.

That and then there's Dark Mind, also with only a 60s CD. If you Dark Arts this combined with Shadowskin or Shadow Wall for any magical tank buster like Discoid in A4 or even (sorta) the constant prey wave attacks in RavEx, you take a pitiful amount of damage. Even less with Delirium and Reprisal up. In RavEx I pop Shadow Wall for the first set of attacks, and after the orbs go out, try and see if i can have Reprisal and Delirum up, and pop Shadowskin + DA Dark Mind. I've taken under 1000K per hit without any mitigation from healers.

Basically DRK has two big mitigation cooldowns, two decent cooldowns with very short recast times, and 4 cross class abilities for seasoning.

As for DPS, people are getting too salty about C&S usage. Basically if you just Dark Arts'ed two SE combos in a row, and you follow it up with unDA'ed C&S, you've just bought yourself another DA SE combo. DA SE is only 50 potency less and is usable every 3 GCDs.

There will be situations where if you DA SE and then DA C&S before your next SE, you won't have enough MP to keep DA SEing. its really dependent on the fight, and fights are so varyingly mechanic-heavy in new content I never would claim something like C&S usage to have an end-all-be-all strategy uniformly across every encounter. It depends on a crap-ton of things, how much damage you're taking, how much your DPS aren't watching their hate, your MP, and so on. But essentially if all other factors are equal, there are times where I've been able to DA 4-5 SE combos in a row, while using unDA'ed C&S, whereas had I DA'ed C&S, would not have been able to get off more than 2 or 3. UnDA'ed C&S is like a free Syphon Strike. It has its uses. If you're ever hurting for MP bad enough to use unDA'ed C&S, it should be because you've been spamming 400 potency SEs and want to keep doing it. 50 potency isn't always worth it.