Or a red mage + white mage, or red + black.
Basically, I like to balance my FFI party with 2 physical characters and 2 magic-based characters. However, I think using 2 red mages as the magic characters works better than having a white and black mage, since red mages actually have the potential to do damage without consuming magic power-- not to mention with two of them, you can have a variety of spells as well. The other two spots can have any combination of physical fighter.
What do you think?