This is likely the cause of at least some of the complaints people are making about frame rate hits in DX11, at least if your frame rate in DX11 is exactly 30 fps (it will likely be higher if you turn of vsync).
There is still a performance hit with DX11 though, without a doubt. My frame rate is about 20% lower using the same settings and just going from DX9 to DX11.
Edited by TostitoBandito, 04 March 2014 - 04:40 PM.