Holinka tweeted on some information about arena popularity.
To be quite honest, the bottleneck is spinning up games fast enough. A lot of people are queuing. We're working on a fix right now.
This is utter music to my ears. Thank you so much! I was starting to worry WoW PvP was dying, but far from it!
Just to bang the "people love rewards" drum a bit more, 3v3 has seen a big jump (probably do to the mount achievement).
It's mainly due to the 2s experience being so bad, imo- people cap in 3s instead.
2s is doing better than usual as well