I've struggled into the exact same problem...
It seems that it has to do with some EFI Update the rMBP recently received.
Try to do a SMC Reset (Shut down rMBP, Press left Shift Button+CTRL+ALT+Power Button at the same time, wait a little bit and then start your Bootcamp or MAC Partition), it will help!
Thank you for this suggestion. It worked wonderfully. Now I'm getting between 40-50fps in Skyrim and my other games are running smoothly too. I really appreciate your help.