I just played through FF1 with a party of two fighters and two red mages, and it was the easiest game I ever played. Why? Because my two mages didn't spend 90% of the game stood in the back row hitting for 1 damage while I saved magic for when I really needed it!
Sure, they can't learn Nuke, Fade, XXXX or Zap!, but why does that matter when you can rarely afford to use those spells anyway? Chaos went down in a couple of rounds and it might even have been quicker if I hadn't wasted time casting Fast and Tmpr...
So in conclusion, I think the Black and White mages kinda suck. What's the point when they're only useful in 10% of the battles, as opposed to Red Mages, who are useful in nearly all of them, especially when they have nearly as much HP as the Fighter? Hooray for Red Magic!