Um. Well, the entire mounted setup in TES is now and always has been - uh.... "marginal" is about as polite as I can get I guess. I can't even imagine how bad mounted combat would be.
Even WoW, as mount-dependent as it is, doesn't do mounted combat for the most part (and the few times it HAS, it's generally been a disaster for anyone on less than a T1, since lag can be a HUGE issue - the Tourney comes to mind, where if your lag is anything over 40ms, you simply can't compete.... literally).
And since "knight in shining armor" isn't my idea of fun in a game, I wouldn't be using it if it WAS included in Skyrim.