Early on, I did this:

Bartz:Knight

Reina:White Mage

Galuf:Black Mage(I tell a lie, I went crazy giving him jobs, but I shudda stuck with BM)

Faris:Knight

later on:

Bartz:Still Knight

Reina:Summoner

Galuf:Time Mage

Faris:Still Knight

People may say this is cheesy or lame, but it isn't. I took down the last boss with the lowest stats I have seen on this forum (I posted them somewhere on this board, have a look around on the last two pages referring to any stat-based thing)

Obviously, I did make characters different jobs occasionally for different challenges. For some reason, my Reina is a Lv 6 thief!