Well I'm not arguing that a priest is a extremely tough fight for a warrior, but generally most people underestimate warriors and get quite a shock when the warrior starts winning
My level 35 killed a 43 undead rogue the other day
although I did get healing from a guild mate.
Edit: I've never really seen a mage been too powerful, generally we take one along because polymorph is extremely useful. It could be worse I guess, they could be warlocks