Weird. I have it set at everything max, except for MSAA at 4, and the game is very playable for me. I can tell there's a small difference in framerate sometimes but nothing that comes close to being even slightly annoying.
It seems like every game has a certain feature that can cause huge drops in FPS. Witcher 2 had Ubersampling, BF3 had Ultra Textures that without 8gigs of ram would kill your fps, and plenty of other games have this too. One setting to reduce or turn off that makes everything normal.
1920x1200, DX11 Ultra with 2xAA = 45fps min, 60+fps average, silky smooth. Just drop the AA, force FXAA/MLAA if you don't mind the slight blurriness in exchange for a smoother frame rate. Or you could inject SMAA and see how that works.
I have GTX 680 4GB version and I get around 40 FPS with everything max + MSAA x4. My problem is that the game doesn't feel smooth at all, 40 FPS feels like 20. Never got this feeling from any other game. For this reason, I'll have to turn down my settings for 60 FPS and see if that makes any difference.