Mine was:
Terra- main magic user, perhaps strongest fighter as well (minerva and aegis shield helped too)
Locke- got some items, used the wing edge weapons in back row as a nice addtional fighter
Edgar- Tools and secondary magic user, another powerhouse for me
Setzer- genji glove and offering = doom darts and fixed dice = kefka dead in around 5 min

it was so simple to beat kefka with this party..I didn't spend time getting the best armor and stats so they were kinda weak except Terra who kept everyone alive with Life3 and all her magic

Everyone in that party knew most of the cures, the elementals to at least lvl 2 and of course rasp and osmose. I used them to beat everyone even all the statues (kept exiting and restarting of course )

The rest were alright, just there to get through the tower and to say they did it together (started together and ended together...yay)

perhaps it might have helped with the economizer but i just never thought about getting all the side quests so yeah...(i don't ever remember what level i was when i beat the game )