So far there are characters that seem to be more suited for certain roles, though I can only really speak for Balthier/Fran/Penelo. I ditched everyone else >_>. Though honestly the only deciding factor is MP. The less MP they have, the better for quickenings. The more they have, the better for magics.
But yeah. So addicted @_@. Though I'm probably pretty overleveled since I keep hearing about how all these bosses were so horrible, and I mostly just normal attack bosses to death Dx. Mateus was a bit scary at first (OMGWTFSIXELEMENTS?!), but once I got a decoy on Balthier it all went fine. <3 Matyr and green/white magic =D. The second judge you fight was a bit scary, since after I got him down he started running up to a character and whacking them till they died.
<33 Balthier :].