Two fighters has always been overkill for me in FFI.
I tend to favour a combination of mages with a thief for quicker kill tactics, though I'm often about all out attack in any RPG that allows me to play that way well.
Black Mage + Black Mage + White Mage + Thief
or
Black Mage + Red Mage + Thief + White Mage
have been my most common setups.