Running both DRK and WAR in a comp that has a NIN, the DPS is about the same between the two classes, BUT, DRK is higher in a purely MTing capacity. This is assuming the WAR stays in Defiance and uses Wrath for Inner Beast.

Honestly I still feel squishier on my WAR than my DRK, but DRK definitely takes way more focus. Since the other tank in my comp only plays PLD I've been going DRK since we have a NIN.

Since I've yet to perfect the rotation for DRK I'll probably go as WAR into Alex the first few times, but eventually swap to DRK once I know the setup.