Thanks! I have the exact same CPU and overclock as you and was having problems after the latest patch. I'll give this a try. Another temporary fix that worked for me was to simply alt-tab out and then back in again. The framerate issue comes back after about 5 or 10 minutes though.
Core i7 5820K hexa-core @ 4.4 GHz | 16 GBs 2400 MHz DDR4 | Dual MSI GTX 970s | Dual 128 GB SSDs