I have used them all before, yes.
But since I only replay the NES version I'll never use a BLM or THF again.
The other characters I mix and match depending on how I feel. Generally if I'm just going for a playthrough I'll use FI, BB, RM, WHM, but some of my more interesting parties were FI, FI, FI, WHM and Fi, RM, RM, RM.