[chocozilla]

I'd say:
White mage - Really great for healing and you can just put them to rear at the star of battle. They can also cast protect and a few offensive spells.
Archer - I just find that this class make it much easier to fight against bosses. They're great against flying enimies too. They have decent armour and, once leveld up a bit, they are very powerful!
Warrior - They have high attack and defence points. This makes them useful in battle and they can use nearly any weapon and armour which you pick up throughout the game.
Evoker - Summons bigass monsters and can be put to rear at the start of battle so it doesn't die too easily. Very powerful beast summons.