There have been buffs and nerfs all throughout the history of crpg, but none like this...either for cav, inf, or ranged.
Imagine you are a cav, or an inf...and you damage is instantly reduced to -33%, except headshots...and the other classes were left as is. For real, imagine it! I play cav and inf, and it would completely change the game for me. I'd have to be a "head hunter" and I'll probably play Rageball only or just quit. It would not be fun!
That's what ranged players are dealing with. It's a totally undeserved and unprecedented nerf.
Then I would probably make all the possible efforts and learn to aim for the head constantly. It isn't that difficult in melee, especially with a 1h.
Cavalry were pretty damn strong before that nerf. Ranged were strong but mainly in groups and they had unfair advantage over others (roof camping). Single pro archer could kill a lot but that wasn't even near to what pro cav can do. And for cavalry you don't have to be pro, you just need to hunt unaware people.
For cav, part of being pro is that, hunting unaware people. Since cav is more heavy than other classes in autobalance due to high equipment value, we have to do more killing than footmen to be equally effective for our team. And I'm not even counting the fact that out of all the people cavalry kills, there are way more noob victims than actually valuable players, because those have developped their awareness. This isn't the case for infantry, and even less for ranged (ever noticed how many good players go on rampage then die to ranged ?). Cav don't choose their kills, they go for the opportunities.
Furthermore, there's a reason why the pro cav end up with average 4/1 ratioes and bad ones with average 1/2 or worse, and it is the same for all the classes : skill. However, cav skill isn't comparable to melee skill or ranged skill. Cav is mainly about timing/anticipation, planning, game reading and awareness. If your definition of skill is limited to twitch reflexes or accuracy, then cav is not very skillful.
It is weirdly a much "slower" type of gameplay because events happen without being really connected with each other. During a match, a good cav will interact with a much greater part of the enemy team than any other player, but all these interactions will be extremely short and completely unrelated (although probably very intense, resulting in the death of one player in case he fails). Unlike a melee fight where everything is a consequence of earlier events. The main difference is that due to the speed of the horse (and the horseback attacks) and the lack of maneuver, you need a lot of time to correct your errors, so when you take a decision, you must anticipate everything that will happen in a rather large time window after the moment you took that decision, because you'll have no way of changing it.
Different skillset, that is all, none is really superior to any other IMO. If melee fighters all had the same weapon, couldn't block and had to start their attack nearly one second before the impact, those with the best timing would dominate and would indeed be the most skilled.
