Just remember that you can't use magic inside Oeilvert. That makes my decision pretty easy. Of course, it's still up to the individual. Amarant's a plus for Oeilvert, because he can still use Chakra to heal, and the chemist ability makes Steiner useful with hi-potions. I've had no problems dividing the parties between strictly physical and strictly magical groups- the areas are kind of set up for that strategy. You'll probably use a few ethers going through the Desert Palace, but it's nothing to worry about.