Heya, I’m having the exact same issue. Ironically I also have a 6970 also, running on a i5 2500 cpu. Have always sat at 80-90 fps on max settings, I cap it at 60 and vync etc. I reinstalled windows 8 two days ago and that’s when my issue began, although I don’t have this issue on other games, only Guild Wars 2.
To my solution. Uninstalling Catalyst and the drivers then reinstalling fixed it, but a day later, back to square one with the issue. I’m just going to sit tight for a gw2 update, hopefully it’s just a bug, like the one they had with the texturing lines on the 7xxx series cards.