I started only about 2 months ago on this server so i only know a little of what kind of madness was happening to incite these measures in the first place, but I feel like recent blanket changes cause more problems than they fix. Since the changes went into effect, only WSG games happen in the 20's bracket. I imagine this is because wsg requires only 10 players and always seems to be going on- players would rather be playing than waiting. Low level players want to que for battlegrounds, and accept the first one that pops, but it is less exciting to que only for wsg because you know that AB probably won't happen. Rather than waiting around for 10+ minutes or playing monotonous strings of wsg games, one might as well be out levelling and thus, fewer games happen overall.
Frankly i don't have a well thought out suggestion for fixing max level pvp, but please compartmentalize whatever measures are taken to affect only that which is broken. Else, you risk breaking more as i have observed with the 20's bracket. I suggest that multi-que be allowed again in all levelling brackets as soon as possible.
Just keep in mind that most players will almost always take the path of least resistance. Please try not to create resistance where it is not called for.