Did I ever say overpowered? No. I said "imbalance". That can go either way.
From what has been said and the way you said what you said, it's pretty obvious you meant that it is over powered, because the other way it just doesnt make sense, who forces you to fight on horse back in a mountainous area and that way imbalance your game? Was that really, honestly, your point? My point however is that at some places mounted comat will work in agreat way, in the mountains however not so much, but it's still not worth the effort.