Good news for nvidia users, I just tried out the latest beta nvidia drivers 310.14 that have threaded optimization and they do make very measureable impact on performance if you enable that feature.

This is using drivers from the bleeding edge xorg-edgers PPA so use at your own risk. Eventually they should hit the X-updates PPA.

Info taken from the botton of:
Launch command I used:
LD_PRELOAD="" __GL_THREADED_OPTIMIZATIONS=1 wine wow.exe -opengl

Using System Monitor, Wow.exe now uses about 134% cpu instead of 100% without optimizations enabled. Also history of cpu core usage is flat instead of alternating up and down.

I don't have anyway to compare it with the old rGL patch since it stopped working for me when MOP launched.

I don't have guildwars 2 but if someone who does wants to test this out and inform GW2 users this maybe what they've been waiting for.