I think by my 13th or so playthrough, I was trying some magic exclusive formations. Eh. They work. It'll just take alot out of you. It was long ago, but I remember having to be pretty buff heavy to over balance my classes. You can play through the whole game with all mages, and depending on the circumstances given in a battle, you can finish fights in fractions of the time it would take you to work around melee fighters, to set up the right spell in the right place and timing is everything.

... I miss this game. Its been years. Gonna have to grab it on psn when i ship out my ps3...

As far as 'on topic'; I can't weigh one over the other. Your mages are artillery to your ninjas infantry, or your knights as tanks. You can blend and balance, but get the same results at the end of the day by going heavy off balanced.