When I use horse archers I use the steppe riders, and if I have acces the arosi riders. These are the horse archers which also have a lance that can get a pretty decent charge going. What I do is I charge say a phalanx unit from the back with one unit of my steppe riders, and when the phalanx unit turns around to meet the threat I unleash about 4 units to its back. The phalanx instantly breaks even the elite phalanx units. I dont use the horse archers which have a little dagger for melee the steppe riders when charging in numbers say 3 units and up break anything.