Tbh:
- nerf HP of all horses to some uniform number - the armoured ones are protected by armour already, the double durability buff made sense with piercing accurate archery, now it doesn't, since now armour is actually protective, and the extra HP enables you to screw up too many times by driving into pikes/spears and riding off merrily
- the riding skill made all horses faster - partially it's good because it distinguishes people who've invested into riding a horse from the ones which didn't, but it also gave them all a buff which is slightly too much - shaving off a point or two of speed/agility to get them more or less back to old speeds (or only slightly above with high riding skill) would make sense
I've got a level 30 lance horseman (on a light horse) and, well, the single biggest threat are other, better lancers (since lance vs lance fights, someone either loses a horse or dies in one hit), then HAs (because they kill a normal horse in 2-3 arrows and can follow you around), throwers, then foot archers with warbow & longbow and crossbowmen. However, it is - in absence of all these things, and on appropriate maps, really really powerful.
Also the LOC needs to go away for good. It's a stupid, silly weapon.