15 FPS - is it even worth it?
I would say no, Not sure why you would expect much out of specs like those. Even in a standard pc rig with those specs 256 mb of graphics is terrible. Most any games take to run well at least a gig. You’d be hard pressed to run something like Facebook games with those system specs let alone a graphics intensive mmorpg.
Actually there are plenty of things that will run justified with 256mb of graphics memory. WoW or GW1 for example...
Unfortunately GW2 is quite demanding, especially the osx port. If you don’t have access to another machine then unfortunately gw2 might now be for you :S