At the end of the game, magic is pretty pointless. Any attacker can kill most enemies in one hit, and the Red Mage/Wizard can as well. By the end of the game, I find the most useful spell to be FAST. Red mage is the only mage I even consider taking when I play the original anymore, because Black and White mages are useless. Of course if we're talking DoS, or some other version, sure I'd take another mage, but not in NES version where magic is so limited it's worthless by the end regardless of what class they are.

THE JACKEL