My spec FX6300+990FX + Driver 15.7.1
If I run with DX9 or Opengl is normal can set at FullHD with Fullscreen mode,but if i run with DX11 have a problem.
I have check with my laptop with Nvidia VGA,it normally can set at resolution at Full HD with DX11 in Fullscreen mode
no any problem.
Then I think this problem is AMD Driver please fix and make optimal catalyst driver for Dota2 Reborn game in your next