Show us that even players with mediocre skill can hop on a horse/xbow and do well.
Actually that's the problem:
They don't do well. You just can't kill them. And as long as they are riding around, incompetently firing bolts into the wilderness, they "aren't leeching" and the round just drags on. It's archers on roofs but at least with archers on roofs, everyone can bring a ladder. Not everyone can ride a horse.
So yes, even mediocre players can be an HX, be 100% ineffective on the battlefield and still drag the match out just by avoiding everyone and firing from 100m away.
I've seen more draws in the past month than I have in my entire previous 10 generations. My complaint is not that HX are overpowered -- my complaint is they have no natural counters and frequently turn matches into a draw despite absolutely no chance of winning. When the match is 1 vs 12 with 2 minutes left, that HX doesn't even have enough time to kill 12 people, especially since even the good ones have a hit rate of maybe 1 in 5 shots.
HX is not an effective combat class.
It's a troll class.