I have an nvidia card myself and get amazing framerates with everything maxed. I had no idea it was that bad on AMD.
Yeah it's pretty ass. Dev is blaming AMD wholly, but it seems to be a problem with the engine more than anything, if you unlock the FPS on an Nvidia card/other drivers you'd notice a huge frame-drop in Hyper Cruise too, just that it manages to stay above 60 for the most part if the drivers aren't enhancing the problem.