I think there needs to be another tanking class for starters... probably some kind of barbarian that dual wields, as that would not only appeal to a huge number of players, but would also fill what I see as a void for 2H dual-wielding classes (I'd simultaneously broaden the weapon types usable by Warriors to like... 2H swords and 2H maces and mauls, etc. The 'just axes' thing is silly).

I might also add some kind of shape-shifting class of some kind, although I would go to great lengths to avoid making it too similar to WoW 'jack of all trades' druids. There's also room for another healy type class.

One thing that might be neat is to give all base classes two advanced jobs to choose from. So a Gladiator might get to become either a Paladin or a Knight... or something like that... Lancer -> Dragoon or Pikeman, etc.