Now i think about it i'm pretty sure i used to run this game on a 4790k, so i'm not entirely sure it is a cpu bottleneck, and i have always ran at 2560x1440p at high frames.
The only things i can suggest is:
Downgrade your gpu drivers and test a few old ones.
Update your windows or if you recently had an update restore it back before the update.
Upgrade to windows 10 if you haven't already.
Try out a different monitor or tv, better and higher res would be ideal if possible.
Turn off DX12
I will see if i can find out more and let you know if i come across anything useful.
