In any case, I think the game should react on the chosen playerclass in some way. Like, you are a mage now, you are super powerful because you are a mage, nobody can really harm you, yadda-yadda. And in return now, the gameworld should react on you in the same way, like... I don't know... nobody really likes to talk to you, traders are giving out their wares to a much higher price and whatnot. This way you are keeping some balance and still give the player a different feeling while playing.