Why exactly would riding and firing a bow while riding cost the same? Makes no sense from a game balance or realism standpoint. Obviously if riding is a challenge firing a freakin bow is WHILE riding is going to be a lot more challenging. And horse archers have always been one of the most powerful classes on any cav playable map. Because unlike archers they can fire on the move and easily outdistance anyone but cav.
I think the current balance is fine. With riding being 3 levels per skill point you can actually work out a balance where they aren't totally screwed on the ground. Before with every six levels.. not really. An HA can still fire his bow fairly well on the ground. Not as well as a ground focused archer but still effective. Why shouldn't regular cav get a shot at being effective too?