Actually in real life a human will beat a horse in a race if its a short distance.
What I would love to see is horses accelerating slower so that if they do make a mistake or get stuck the infantry can actually get at them.
As far as running xbow users, I would say raise the strength requirement on xbows across the board.
Those bloody things are actually really difficult to load and do take a lot of strength. Since the weapon requires no skill points to use, it should only make sense that they are expensive and have a steep stat requirement.
