Take this with a grain of salt. But I've heard people say Ryne is the best at... "sustained" DPS. I've also heard people usually prefer Alphinaud to Urianger because of Alphianud's shields and a damage buff he can give you.

Probably unrelated in some way, but I've seen Alisae cast "Vercure III" when things got really dicey. Healed all of us fairly good.