I think the guy at 50 should be able to beat you - but only if he's trained his players correctly, and has a good strategy. Problem with MB in the championship is not so much that it means he can beat you, but more that he can't beat you if you both use MB. With 12 difference, if his players are trained in key areas and his strategy is right, he should have a chance. But if you both whack on 100% bonus, the difference is 24 and he has much less chance. Of course if he's not gone to the trouble to do that, I can see why you might think he shouldn't be able to beat you. In championship games it doesn't matter because you have the option of putting it on as well. In GvG, I can understand your point of view.
I don't think there should be tiebreakers, though - if this imbalance is corrected, I think there would be enough straight results anyway. FWIW, my guild's record is 24 wins, 15 draws and 0 defeats, and we're not huge MB users, preferring to do it by tactics and make money from GvG (I made 15 million from it yesterday with 2 home games and 4 away games), so it can be done even now.