Rolled a 5 man team consisting of 2 hunters, a warlock, priest, and warrior leading the group (don't ask why) and it was working granted the team is only lv20. As far as a duo or trio goes you could always roll with a priest and just have him healbot your warrior, use your 70s to keep your warrior in the latest gear and you should never really have down time. I'm sure somebody here has more insight into this but just thought I'd throw in my two cents.