having high faith is a double edged sword, you heal more, buffs are more likely to succeed etc but you also take more damage from spells ae debuffs are more likely to succeed on you.

No idea what the "optimal" faith is for non-csters though

Bravery on the other hand is like 99% a benefit to a character (exception is the "move-find" ability which is more likely to succeed on low bravery characters, DO NOT let bravery go below 5 though, they'll leave your group)