Pix' idea is much more interesting, clearly he's actually put more than 5 seconds into thinking it up.
Rather than making every class be able to kill the same mob in the same amount of time, we SHOULD be trying to change the speed of the kills.
Hunter/Mage's should be dealing LARGE damage, and closing down fights fast before they take too much damage themselves.
Warrior/Priest's should be dealing LOW damage, and slowly wearing their opponents down, being able to take significant damage without feeling much.
Ranger/Esper's should be dealing MEDIUM damage, and evading more attacks than not.
Thieves should be able to perform CRITICAL damage with backstabs, but be almost useless at hand-to-hand combat.
Gypsy's should be trying to convince people not to attack them...
Your suggestion is going the wrong direction Bane, you just want every class to be able to kill all the same mobs in the same period of time. Bad strategy.