For a six box on Mangler, I rolled with Paladin/shaman/druid/bard/monk/mage.
Knowing what I know now, this would be my six box: SK, Enchanter, druid, cleric, monk, mage. I think having a bard box is very useful but I don't think it really shines until Luclin, to be honest. Plus they're super easy to PL, so can always make one later. I prefer druid over wizard for ports/evac because backup healing is useful and their dots are very good (as are their debuffs later on). If you want to take down high value targets (like hate minis, for example), you're going to need efficiency. Wizards kind of suck without FT and focus to elevate them. It was dumb not to have a cleric originally -- they're just too damn good at the primary job of healing.