In my group, we decided that a single class of anything is better than any multiclass, because if you have 4 people in a party, and all of them are 8th level, and one is a 4/4 fighter/thief, and the others are all single class, the EL's for the party level outstrip the fighter/thiefs abilities...AKA, the DC's are higher than a 4th level thief can manage(most of the time, ie unless the thief is extreamly lucky). I remember reading something about "if you have a new charachter don't make them more than 3 levels lower than the party" somewhere. (I think the DMG???).
Just a thought.