which game are you playing mate?
the 960 should perfom better than that and like i said theres nothing wrong with your cpu...
gt 720? you dont have both in the case?
if so make sure the 960 is the primary boot card by selecting its pci-e slot to boot first in the eufi/bios or better still remove the gt720
fact is mate im wondering if thats not the problem as 20 fps on medium settings on a game like bf4 would be ablut right for a gt720...
when you say you uninstalled the drivers?
did you also clean the registry and remove any leftovers with a dedicated driver cleaner? if not give driver sweeper a go.
http://www.guru3d.com/content-page/guru3d-driver-sweeper.html
lastly try loading optimised defaults in bios. then set the primary gpu to the slot that has the 960. set your drive boot order and reboot.