What mine usually do is rush forward RIGHT at the enemy, run into them, hit them once, then sit there getting their ass handed to them by the swarm, not even trying to ride away. Be nice if they could be coded to ride at the outside guy, and pass a bit to his left or right, so that they can hit and keep moving instead of stop.
Also a problem is when mounted units go against mounted units. I put Marnid on a spirited courser with a great lance and steel shield (and black armor, etc) but he still dies miserably, because hes an idiot. If a mounted unit gets behind him, he slows down trying to poke backwards while the guy behind him is beating him down (and he cant even point his lance backwards). Be nice if they were made to speed up (his courser would be faster than their horse) and then turn around to rush them in the front. And against ground units he *never* uses his couched lance - he just rushes into the group, gets stuck by one of them, and stands there poking till they surround him and beat him down.
Ive noticed the same dumb maneuvers in the arena mounted units - they will run into a wall and sit there while you stand behind them beating them. They just sit there poking the lance as far back as they can point, which is not even close to you. Can also run up behind them with a 2h sword and horse and hack them up while they slow down trying to poke you with their lance, which cant reach behind them. And if your the guy with the lance you can run up behind the guy with the sword and he slows down and lets you poke him to death.
All of this is with AI set on good, so its not like I have it set on poor and want it to be bad lol.