Strange, I feel the horse combat is very usable and I haven't really had any trouble with it. I still need more training using ranged weapons from horse, but I am usually able to hit my enemies when I am using a melee weapon, even if I am galloping(yes, you can do both at the same time

).
Same here, I find it simple for melee but I need more practice at archery from horseback. I dont run around in circles though, I do laps back and forth using the sprint. Line em up, attack, sprint away, turn 180, rinse repeat. Its only tricky like this when its beasts like sabercats who are fast and can keep up, though if you are smart and attack at oblique angles the AI can get funky and attack mid air each time trying to hit you.
Though there was one fight where a sabercat managed to kill my horse while I was sprinting with it. Pretty funny to see my horse die and my character take a nosedive to faceplant the cobblestones in a stun animation.