I have this setup:
Butz: Dragoon (Duel Wield sub ability)
Lenna: Ninja (With X-strike of course)
Faris: Red Mage (Sub: Near maxed out black mage) working on dual-cast for obvious reasons.
Galuf: Summoner/white mage (nothing special here)

Gotta say, Ninjas with X-Strike (Rapid fire in some versions) are overpowered.
So far I would think this game very easy to break with some patience and planning ahead. Still it's brilliant.