This is how cross-Battle.net Dungeon invites should work.

A marine would do 6.97 DPS, and a marauder would do 13.33 DPS, or 26.67 DPS on a boss (I'm assuming bosses are armored). With stim, they'd increase to only 10.5 and 20/40 DPS, respectively. In a level 80ish dungeon, that's less DPS than a healer hitting the boss with their melee. I think I'd rather do a dungeon with Ronnee, who apparently has my mother's tattooed eyeball.