Is it a matter of having your own subforum, or the potential audience? If there aren't a lot of people playing other games, making a seperate forum isn't going to make those people appear. Perhaps a WoW discussion forum would be more appropriate so that General Discussion can remain about general multiboxing topics, but without so much of the WoW clutter.

Then again, we have WoW PvE and PvP, so I guess those already exist.

Sorry about the situation, but the nature of the biz is that most people play WoW.