Taking the GK clan out of the equation for the moment, the fact remains that there is, and has been for a long time, a flaw in the way that the game balances cavalry.
I admit that in recent weeks I've only played Eu1 when 2 has died, so the server often has only 60 players max, but time and time again it is the case that an overwhelming majority of cav players will be on one team, regardless of banner, etc.
Even more oddly, when the game decides to switch a player to deal with imbalance, it almost always switches an infantry player from the cav dominated team, which is almost entirely ineffective and does not address the imbalance within the teams at all.
Clans stacking to win constantly is/has been a fact of life on this game for a long time and I have no major issue with it, I won't begrudge others the extra teamwork, etc that they have worked towards, but as I've said, an issue remains with the balance of cavalry, the GK thing here serves to highlight the problem perhaps, but talking about clan/banner balance, etc, is wrong as it takes attention away from the fact that there is a flaw in the balance system that has nothing to do with those things.