I'm inclined to say for a dungeon run drk has less buttons to juggle than pld or war, but I haven't lvld mine to 70. For aoe situation drk spams abyssal drain with dark arts, ogcds and defensive cds weaved in, pld does flash 1-2x and spam total eclipse with ogcds and defensive cds weaved in, war spams overpower while maintaining eye buff and occasional decimate spam in berserk/inner release, while still having to weave in defensive cds. On bosses pld needs to manage 3 combos (halone, royal, goring), while weaving in requiescat and holy spirit spam. War is similar with the 3 combos (eye, path, block) and on top of that war needs to manage gauge and align berserk/infuriate/inner release. Drk only has 2 combos, and dark arts usage is pretty easy (carve and spit > everything else other than dark passenger).