Actually, it's not a problem anymore for
SOME people to be heavy cav, but it's really sad that it will ruin you and more importantly fuck your autobalance consistantly.
Autobalance is influenced by equipment value, so if you are using a horse, you are better doing at the very least 2/1 k/d ratios because you and your horse are nearly as costly as 2 footmen.
The dev team says it wants diversity yet being heavy cav is impossible for most and completely dumb for the rest.
I like your comparison with archers.
Honestly if you look over at archers who can't even carry multiple stacks of their second best arrow without going broke, cavalry have it super good.
So now to get the picture about cav, imagine that your bow alone makes you go broke.
Furthermore, PC and other tank horses don't give immunity to damage at all. I would even say they are more dangerous to ride than other horses. First you have all the enemy lancers that will try to poke your back and will do very easily. Second you have the pikemen, xbowmen, throwers and archers that hear you coming from a mile away. In the case of pikemen, if you are stopped near 2 or three enemies, intelligent ones will hit you first and even in full plate, 4 or 5 hits of 2h/polearms will kill you. Your horse didn't even helped you in that case. Ranged classes are also a problem. First they can dodge your charge very easily, and second you can only rely on the charge damage itself, as it's easy as cake to hit the rider of those monsters (that's why tank horse riders all have shields). And still, only PC can
survive an arbalest headshot (next hit kills them).