I want to add some personal anecdotes to this thread, because I play both WAR and DRK extensively, and I'm also a dungeon aficionado.

I play with my healer buddy, and I know I've made mention of this person in previous posts in other threads, but they do run a parser. However, they haven't really played in a few weeks, so i can only give out results from 4.3.

That said, by the end of the dungeon I've noticed the results are fairly consistent, and they should be given that I play the same way every time on both tanks. But normally on WAR I'll do something like ~5k, while on DRK i'll do something like ~4.5k. To me, that difference doesn't allow to say DRK is suffering in the dungeon department.