I hope this doesn’t upset the mac Devs, but I was playing around with the Cider config file trying to improve performance. The one setting on my system that made the most dramatic improvement (8-16pfs increase) was setting “MTD3D=1”. This is the config file in your <home>/Library/Application Support/Guild Wars 2/ directory.
Disclaimer, I do have a i7 hackintosh, so your mileage on a real mac might vary.
For a frame of reference, running around in the courtyard under the large glass dome in Divinities Reach, I’m getting a solid 45 – 55fps with MTD3D-1. With it set to “0” which is the default, I see around 30 – 38fps under the same conditions.
My box is a i2700 @ 4.5 Ghz and a GTX 680 using the latest Nvidia drivers for 10.8.2.
I’m driving a 2560×1440 display with all graphics settings set to High/Ultra.

Please be smart and make a backup of the file and if you experience unusual crashes, revert your changes.