I don't usually give input on balance when I have not played a game very long (only gen2 almost gen3), but here's my take on this. Cav aren't "OP" in the sense that most people would define that term. Cav ARE "gay" in the sense that most players would define that term. Basically, it goes like this. If another player is able to get a kill (or even worse, many kills) without visibly performing better than another player in combat, it's gay. Now, I'm not claiming that cav "takes no skill hurr durr". I'm claiming that cav does not require the user to perform visibly better than another player in order to get a kill. Same thing with archery and crossbows, and to a lesser extent, ranged.
Now, I don't feel that you can nerf something just because it's gay. If the devs were to implement a patch tommorow disallowing reloading of xbows on horseback, I would not mind a single bit. I can't stand fighting HA and HX because unless you a range player, they can simply choose to not be in any sort of danger. However, if there was a complete axing of HX, I feel that all those former HX guys would just go HA. I don't feel that the devs could then justifiably remove HA from the game as well.
So, I don't think that a "nerf" or "buff" is the answer to the cav "problem". If any solution is to be made, it would have to be something that discourages people from playing the class, but still allows them to do so reasonably. Price increases are the only thing that comes to mind, but I'm also not a very creative fellow. Maybe someone else has a good idea. That's my 2 cents.
Oh, forgot something. I don't go on EU very much since I'm in NA with a god-awful connection at the moment with no need to set foot there. Great Khans came in the NA server with about 5-6 cav players (mostly very skilled HA I believe?) and fucking WRECKED EVERYONE. If you weren't on the GK team, you had to enjoy your 1x or quit. I chose to quit, there wasn't a thing I could do about it as I wasn't ranged. I went longspear/pike, but that only prevents them from coming near me. They can still fill me full of holes since they were actually VERY good at that. Point is, I can only conclude that EU actually has that situation come up rather frequently since GK is a EU clan. Jesus christ, how horrifying.