From a tech support on the Mac GW2 forum posted a week ago;
It seems like people are feeling frustrated. As should they. The question is - can they really do anything substantial at this point?
I doubt it. I tried it recently on a mid-2011 27" iMac i5 3.1, 12 gigs RAM, Radeon 6970m 1 gig RAM.
The performance was terrible in my opinion. To get it playable I needed to run it at 1080p and low to medium settings and then it wasn't too bad but it didn't look all that great either. It kind of soured me on playing it. Everything else I run on this machine plays great so far, most recently Crysis at high settings in bootcamp was awesome and looked a hell of a lot better than GW2 despite its age. And that game still taxes modern hardware if you try to max it but on high it still looked fantastic.
The graphics for GW2 seem nice but I didn't think they were particularly remarkable enough to justify being extremely demanding leaving me to think the Cider port is the problem. I did not try it with Bootcamp to compare however. One huge download of the game was enough and I've since deleted bootcamp. It's Mac or bust around here.
Fortunately, I enjoy World of Warcraft which runs on ultra at 1440p smoothly for me. I've also noted that both LoTRO and DDO which are nice looking games run smoothly on this system on high settings.
For someone wanting to play in OS X, I don't think GW2 is worthwhile personally unless you are okay with low detail settings or have the latest 27" iMac with the best GPU option in it. You "might" get a decent experience that way.