White mage.

You take him through rikku's grid just long enough to get steal and item, and by the time you get to gagazet, he's friggin' awesome, with higher white magic than yuna (if you level them simultaneously. I had him with Holy at that point)

You can use dispel with the bosses that you can't use yuna on(like. . .evrae?), and two+ thieves is always a good thing.