The problem I see is, that cata is an old game, most people who join are the ones, who played it on retail or came from other servers.
You most likely won't attract young players (14-18) anymore, because they play other "newer" games.
That's also why every cata server will die one day.
Increasing rates will allow people from other servers to join here and have fun, also it will attract other ppl from other private servers where nothing is properly scripted.
Also, @Aloise, idk why you bother new players / noobs so much. There is not even one 25m core group on the server, where you only have "elite" players.