I think Bard is the most useful dps ofc.
But for a team comp i think
DRG:huge burst damage and strong single target and good aoe damage,can also share the debuff with bard
BLM:huge burst damage,unlimited mana,highest aoe damages
SMN:can raiz,strongest single target dps(IMO),good burst
Bard:Can dps wihout any interruption resulting in a really good dps(even if it's the lowest) and can support greatly with songs.

Team comp like this resulting on a huge single target dps(SMN +melee)high versatility(SMN can raiz,3 range so if a fight is not good for the melee they can help him on that)very high aoe damage(bard song+his aoe+DRG aoe +BLM aoe are just destroying adds really quick) and huge burst damage.