IMO, the mounts are fine, the problem is with some of the mounted units. The light cavalry are fine, but noble cavalry (Riglachs, Toisechs, Frankish Horsemen [?, they wear mail so I'm guessing they're nobles]) are rather underwhelming. They're supposed to be heavy cavalry (by that period's standards anyway) but aside from a spear they only carry a seaxe or knife which aren't all that great in melee, when, being nobles they should use swords, IMO. As things stand, noble cavalry are only good in a charge and will get wiped out soon after their charge loses momentum even when the enemy is fighting your infantry at the same time while, in comparison, 20-30 Old Captains charging an enemy shieldwall from behind while they're similarly occupied by your infantry are devastating since they use swords.
This is what I've noticed in 1.04 anyways. Apologies if RE already addresses this.