Even if you do 5 separate parties, leveling will be AGONIZINGLY slow. I had 5 mages i was messing around with after a hogger raid, and I was still in the rid, and killing equal level mobs got me 3xp each, while non grouped I was getting like 25 exp. Unless you can find some place to farm endlessly respawning mobs, I don't think you will ever get leveled up.

If you do go for it however, Consider a shaman for your healer/rezzer, cause of the self rez. If you have 24 mages and 1 priest, and the priest dies, you are still in a pickle.