Not sure how you get good rates with DX11, but it may be my setup. Running 1920x1080 HDMI, HD 5770 1GB HAWK, 8GB DDR3. Runs fine on DX9 but DX10/11 are a nightmare.

I don't have elbow pain but rather palm pain, specifically the outer parts of the palm that rest on the mousepad. But then again, I am working on cramped space.