Ay, bad choice going with the sage. Devouts are completely superior due to how useless black magic and black/white summons are. Also I figure geomancers would be a pain in the final boss fight since you can't pick what target you attack. Taking out the rightmost target is pretty much a must, especially if you have characters in your party that are weak to magic (like a warrior), so it'd probably be best to have the geo do nothing until you stop getting lightning'd every single turn.
You try to run away. But there's no escape! The enemy tries to run away. But there's no escape!