I agree - I think having the Google+ page has drawn a fair amount of discussion that would otherwise go to a forum. Will be interesting to see if that shifts at all. The separation of Glorantha and HQ works for me.
Whether distinct forums or sub-forums, what I'd want to see is separation between Glorantha, HQ, RQ, and 13th Age Glorantha. I don't want to wade through RQ stuff to find interesting topics on Glorantha or HQ.