If you set the graphical performance to maximum (which means, including all DX11 graphic enhancements), you won't gain any FPS. It depends on the developer how much graphical enhancements they've implemented that determines your overall FPS.

In DX11, if you look carefully, the ground has tessellation, which decreases FPS slightly.

I'm not sure what you're settings are right now though, but since I've limit my FPS to 60, I can't tell whether I've gained or dropped in terms of performance under DX11.