I feel like DRK is good enough to clear content. My main problem with it is that alot of DRK's abilities are generally inferior to their WAR and PLD counterparts. Grit for example, reduces damage taken by 20% and damage dealt by 20%. Shield Oath does the same thing but only reduces damage dealt by 15%. Defiance is a little different so it's more difficult to compare. Shadow wall is pretty similar as well, having the same potency as Vengeance and the same duration and CD time as Sentinel. Plunge has no resource cost, but is arguably inferior to Upheaval in every way. Living dead, while in theory can prevent you from dying for a solid 10 seconds, just feels so punishing to the healers. That and even if you die from the effect of Walking Dead, you still get that nice 300 second CD. DRK also feels a bit lacking in complexity when compared to WAR or PLD. I'd say DRK just falls a little short in a lot of areas and doesn't really make up for it anywhere else, that combined with it being oversimplified, makes it feel lackluster to say the least.