Play up strengths. I find that trying to balance out characters who are not meant for melee or not meant for magic results in less of an effect than if you were to use them as they are meant to be used, especially in Final Fantasy. There is a reason the games are set up into parties; the different characters compliment eachother. Trying to balance out everyone equally takes away from a great party combination that could focus on raising everyone to their strengths.

If you try to make everyone equal across the board, you are robbing yourself of untapped capabilities.