I think you’re all missing the point. The unit itself can be strong, and that wouldn’t be an issue. The real problem is how it’s used.
Let’s assume there’s a fight between two decent players (and no, I’m not referring to the endlessly repeated pattern of me vs. Decker). One player is using Champion Cavalry, and the other isn’t. The real issue is that even small groups of Champion Cav — even sent one by one — reach the front line very quickly and draw all the focus to themselves.
Because they’re unreasonably resistant to ranged units, they effectively become tanks that shift the entire outcome of the battle. So is the only option to make them weaker? No.
What if we had control over target priorities? Why shouldn’t a ranged unit have options like “target only ranged,” “target low HP,” “target strongest,” “target weakest,” etc.? With just a few smart targeting presets, we could greatly improve balance.
For example, archers that can’t harm champions could instead wipe out the enemy’s entire ranged force — leaving the champions to fight alone. Simple trick. Big impact.