MoP is quite good, way way better then Cata. Doesn't quite have the epic storyline of WoTLK yet... but it might be a surprise as the story progresses.

Heroics are doable as a boxer. If you look under Dungeons/Boss Strategy guide there is one person whose tackled a lot of them with a melee group. I leveled whole team together from 85-90.

Peeps complain about pickup quests but overall I think the questing is easier then in previous expansion. Some fun/funny quests as well.

If Cata turned you off of WoW and Multiboxing (like it did for me, I quit for over a year just prior to 4.1), MoP should pull you back in, I'm having the same level of fun if not a bit more then what I had in WoTLK... just be warned LOTS of dailies!