Multiple buildings should not increase queue capacity, it should increase the amount of actions that can be done simultaneously. E.g. 2 garrisons should allow training of 2 different types of troops at once, instead of increasing the queue capacity to 2.
I've read two comments about two different clans being OP, so I will post something about some other ones. "Great sea is OP because it has damage absorption" "Chaos desert is OP because of 'burning'" "Poison water is OP because of it's low spell cost (paralyse)" which renders the other mage helpless. "Dark wood is OP because of silence"
The two other OP complaints were for Ice Water and Burning Hill, so I think I'll leave those out.
Oh look, that makes 6 OP clans! If they are all "OP" that means that it isn't the actual game mechanics, it's just your strategy!