I've tried WAR/Marauder dps quite a bit and I always parse a fair amount below actual dps classes. It's definitely not even with them. That said it's not totally terrible and I don't see why a group with a WAR or Marauder dps couldn't work except for one thing: enmity.

Since defiance and shield oath nerfed to be a flat 50% bonus to threat, a WAR/Marauder in DPS gear is going to be generating far more threat than any tank possibly could unless you hold off by using the maim+storm's eye combo over and over again instead of skull sunder+butchers block. This is a HUGE dps loss when you already don't do as much dps as real dps classes.