You can tell any companion to be any class and they will all perform equally well at it. There is exactly one combat encounter you can run into before you walk past at least some companions.
As for my point, its that youre wrong. Completely. Enemies in the early game, by and large, do not have armor of any sort. By the time you start running into enemies that have enough to need to be burned down, you should have a full party and can strategize more than just "I have a hammer, so everything is a nail".
Using your wizard to target high magic armor foes is actively playing against your strengths. Dont do it if you can do anything else productive with your turn.