Simply put, the Fighter rarely needs healing. A thief has high evasion and needs some healing. Black belts can get hurt a lot, but they have big damage for little upkeep(ie really cheap), and redmage can survive with little healing. White mage needs healing basically everytime it gets hit, as does Black Mage. Basically, unless you have a mage, you really don't need a white mage. A white mage makes it necessary for you to have a white mage. If you don't have magic using classes, the magic a Knight learns at upgrade, and the white magic of a redmage, is more than enough to keep your party of fighting characters alive.

Technically the best party is fighter, fighter, redmage, redmage. I dare anyone to prove to me a faster party to beat the game. Very expensive, but a hell of a power team. You get two casts of the hit all enemies early, as well as two people who can heal. Then after classes, you get two more people who can heal some, and amazing physical damage with all 4, plus magic attack support.

THE JACKEL