Fighter, Red Mage, Black Belt and White Mage is a good party, and putting the Red Mage on the 2nd position increases the chances of the Black Belt staying alive, especially when you combine that with the Red Mage's extra healing.

My favorite combination is still Fighter, Red Mage, Thief and White Mage, though. That one is also good for running away in battles, and since Red Mage shines at the beginning of the game and Ninja at the end of the game, those classes support each other pretty well. Not to mention you'll have 3 white magic users and 2 black magic users at the end of the game. I didn't think the group is weak offensively. My game style is quite defensive, and this group does a pretty good job of staying alive. As for physical strength, you'll have Fighter, Thief and Red Mage, so how can the group be weak offensively with 3 physical attackers?