For another idea, how about Green Mage being a barrier/counter tank? Using shields and debuffs to absorb damage into MP/HP and reflecting damage. Cooldowns could have "bide" style damage attributes where they absorb a portion of the incoming damage and return it to the enemy after a set amount of time, for extra if you've dropped vuln-up or def-down on the enemy before it pops. It's DPS and mitigation could be as one, and it could protect the party with buffs and debuffs.