I know you're not using SLI or gsync (?) so I don't know if this will help you much, but this is my personal fix for perfectly smooth, better performing witcher 3, after A LOT of experimentation and hassle...
http://forums.overclockers.co.uk/showthread.php?t=18677820
http://forums.overclockers.co.uk/showthread.php?t=18677820