I agree, I've seen this problem before. Domination of one fandom, and especially in a way like this (Seriously, any day, look at the flist of CW and see how many posts are of AG origin) put people off from the outside of apping different fandoms. The rp becomes closed off, that fandom becomes more dominant, and eventually you'll get a sort of... implosion I guess.
Nothing against AG characters or their muns, but I think if there was a temporary ban on the characters until we get some more characters of different fandom it'll be better for the game as a whole.