Cavalry in cRPG is only strong in numbers, individually they are a weak class on par with archers.
Very true, when they are riding its not very hard to shoot them, horses are very big targets.
But once you down their horse, and they charge at you with a shield. Its like a 2nd life for them, with the perfect counter. And with the trend of Lance/Polearm builds, they can still be an effective infantry.
And ontop of that 90% of the time when i down a horse, and try and shoot the fallen rider, the arrow simply hits the horse ragdoll.. very annoying.
Luckely most horsemen make the mistake of going in way to deep, or very far behind enemy lines. And are in for a long long walk to merge back up with their team when horse downed. Or they simply spergrage about archers, and make buff cav/nerf archer threads while at it. Fogetting they can most likely still one shot archers, and help out their team as infantry.