Don't know what to tell you. Here's my settings. Feel free to let me know if I can turn them up any higher.
[screenshot]http://cloud.steampowered.com/ugc/595866493109090966/902EB4B56578EB98CC88680C720255B8022E8FBE/[/screenshot]
[screenshot]http://cloud.steampowered.com/ugc/595866493109092849/D7F5FD4CE6EA8EC703A82888925F1743DC3E58D6/[/screenshot]
I'm not going to lie and say "I never get slow downs". However, I almost never do. I tried the spot in Thousand Cuts. Works fine. The only time I ever seem to see my framerate drop is when there are lots of PhysX objects around and I look at a light source like the sun or the moon base and get tons of bloom or HDr or whatever the word of the day is. And even then it doesn't kill my performance, it just noticeably affects it. As a point of fact, since it can't be seen in the screenshots, that is at 1920x1080.
My machine:
i7-3770k at stock
Gigabyte H77M-D3H (yes, that's an H77 chipset)
8gb DDR3 (I'm guessing this is low clock but I'm not sure)
EVGA Geforce GTX 460 1gb
Hard drive wise, I'm running on years-old 7200 rpm drives.