Huey went mad, put him down.
Cav is your friend:
Cav success is completely dependent on the awareness and cohesion of the enemy team. A frontal assault of light cav on an enemy team is a death wish, the only margin for success already is to circle around the enemy to attack the flanks/rear or pick off stragglers. Even having dedicated ranged players mark flanking (light) cav will result in them being rendered useless. This is fine as it is, as it brings a nice risk/reward playstyle to cav.
When fighting more than one enemy, it is a viable tactic for cav to hit (lance/sword) one enemy and try to avoid another by running him over. It is in fact the only way cav can cope with multiple enemies (especially as lancer cav), besides their mobility, and only so if the enemy is not able to rear the horse, slash the horse or kill the rider. Fine too.
Cav is also the most expensive class to play and - just like expensive armor wielding tincans - gets rewarded for the high cost by a battlefield advantage. For tincans it is to be able to absorb multiple hits, for cav it is the mobility and extra hp the horses can soak up. Fine as well.
Cav can suck, too:
Where cav is getting imbalanced and annoying is when you have a lightly armored guy sitting on a fat old panzer horse with a big shield, constantly blocking. Often he can just ride over and out of a group of people without getting hit or the horse being killed. Money is imo not a sufficient balance argument for this.
Xbow cav is another phenomenon that drives people mad because of "slow" fighting style with constant reloads, the bump-shots and the dragging rounds out. I believe longterm there will not be many around and it really takes dedicated (troll) people to even stick with this class for long. A solution for this anyway if needed would be simply to disallow a reloading of all xbows on horseback.
In conclusion: cav is hard and being bumpstunned is racist.