There's a lot of legitimate RW activity outside the mainspace. The SB is in the RW space, as are the WIGOs, and then there's Conservapedia, debate, forum and the talk pages. I don't think it's as much of a problem. I'd be very concerned about the site's sustainability if it was most of the top 100 hadn't touched the mainspace, but other than that, it's not a problem.
Did you read my list? I updated it for February. It is quite interesting. Of course mainspace isn't the only useful place on the wiki (otherwise we wouldn't be calling Mei useful). And I am not in favor of deleting(even if we could) WIGO:CP. I'm just concerned about the future of the wiki, that is all.