I think in games where champ cav are banned, the civs with the cav mercinaries in mass have the same dynamic as the champ cav previously had. Only available to some civs which are the ones that usually didn't had champ cav.
Last time camels worked great against the fanatics. Just back them up in time. Use 2 groups supporting each other. Occasionally use citizen soldiers when they are nearby - but don't chase.
As the game progresses one should move away from only citizen soldiers. Elephant archers or siege towers in mass are good too. Just because a tactic can be applied successfully doesn't mean it's OP.
One could make some game specific balance like here, but I don't think it's that bad. I would even include champ cav in games.