I think we can eliminate just about every healing spec; while they'd be annoying to kill, they don't really do enough DPS on their own to be a serious threat. Tanks certainly aren't doing as much damage since the halcyon days of vengeance working in PvP, but would they do just enough to outlast an opponent? And what about DPS? The arms warrior and frost mage are storied opponents, but who really has the winning combination of damage and survivability right now?
So which spec and/or class emerges victorious if they're all tossed into a ring somewhere and left to fight it out among themselves? Or -- given the high possibility of rogues and druids simply stealthing through the majority of the fight in such a situation -- would a tournament bracket work better? Would someone who outlasts the death match not survive a series of duels, and vice versa?