My most recent play through i'm using:
Red mage
Red mage
White mage
Black mage

I have one red mage setup like a 'time' mage with all buff/debuff type abilities, and heals, the other red mage with some damage spells/heals as well. So far it's been pretty fun, and a bit stronger than the last play through I did that was Fighter/BB/RM/BM, since the amount of healing available in my current party just lets me go on for ever.