I've learned how to get Baurus to guess that I am a pure mage. glargg is right, if you only use the fireball, heal spell and make potions then he will guess right. You do have to ignore the locked chests and not wear armor or sneak though. When I play a stealth class he'll guess either a Bard or Agent, but I make my own stealth class so he can't get it perfect, but he comes close.