Running the game in DX11 on default Ultra setting under graphics I get 72 average and 56 minimum FPS with the internal benchmark test under Extras. Resolution set to 2560x1440. It is very smooth no issues. If I go into Graphics and set all settings to the far right maximum settings for everything I get 54.6 average and 44.4 minimum FPS which is not bad if that internal benchmark is the game at its highest stress level.
Game is installed on SanDisk Extreme Pro SSD quick list applicable system specs. Monitor Asus PB278Q max res 2560x1440.
i7 5960X @ 4Ghz with 16GB Quad Channel DDR4 2800 RAM, Asus Rampage V Extreme MB
2 Asus R290X DCII OC cards they run at 1050MHz overclock DDR5 RAM at 5400 overclock set in Crossfire of course.
Catalyst driver version 14.11.2 beta released today.
If I try and use the Mantle API though I get long freezes followed by the graphics speeding up for a few seconds after like it gets stuck then plays catch up. Not sure if this is a driver issue or what. Maybe Mantle is not working well with Crossfire, I will have to disable Crossfire and try Mantle again to see if that's it. Right now though I'll stick with DX11 as that seems smooth as butter.