The former are excellent at buffing troops; in principle, I mainly use them for that. Well, when there are many of them, it's better to cast spells. The damage output is decent.
I really like the priests, especially when combined with fire elementals. They reliably apply the mark, and the fireball deals excellent damage.
Mages are simply evil. I've always said that.
Archliches – debuffs, cloud, and plague. What more could you need for happiness? True, they have one drawback. Sometimes, you just end up hating them :D
P.S. The Incas suck, and you won't convince me otherwise.