An uncommon issue some players are having is a FPS slowdown. Tyan_ili_Kun the real MVP discovered a fix here it is.
1) Run the "Nvidia control panel"
2) Click on "Manage 3d settings"
3) Choice "Program Settings"
4) Click on "Add", then find the game
5) In column "Select the preferred graphics processor for this program:" choice the "High Performance processor Nvidia"