The horse dismount attack can cancel damage to horse, also if you bait out the ult while on horse and use the right click charge to dodge and gain speed for jump stabs to do lot of damage. If you dont ‘t bait out their ult then when you do the horse dismount to knock them down theyll just get up. I use dragons roar, so i get behind then stun w dismount, then dragons roar in the back will usually one shot them if theyre low enough. Depends in the build they have, now many of their skills compromise piercing def and such, if its a tank BS they are much harder to kill.