DM_Blake |
Yeah, when mounted, you cannot simply dance around lightly on your feet to avoid incoming blows. But dexterity is not just about dancing lightly on your feet. (in fact, that's more the realm of "agility" while "desterity" is more about hand-eye coordination). Dexterity is about dodging, ducking, twisting, turning, maybe even parrying incoming blows (and potentially dancing out of the way, too). You can do pretty much all of that in the saddle.
So no, I don't think the "common sense" boogeyman really suggests killing the DEX bonus in the saddle.