My four-man super team..

Vivi:
Clearly the "nuke" of the party, his spells do uncanny damage and I can only assume his spells that would normaly help what's his face would apply to anyone..

Ramza:
Even in squire form Ramza still has a "mini-Ultima". Which is good enough for me and he makes a decent brawny guy.

Vincett:
The fact of the matter is Vincett is cool, he can transform into several bosses and is just plain bad-ass. You'd be a fool NOT to have him in your party group..

And Mog:
Name me one of the Mog's dances that AINT useful yo..

This party seriously lacks in one major thing: a healer. But considering the mad amount of damage you'll be dealing per round i don't think that'll be a problem..