FPS change over the last couple weeks...
My speed did not drop due to any recent patch.
I had an FPS drop when I started using the 64 bit client but this turned out to be my Raptr game optimizer decided to raise game to highest quality from balanced.
FPS after was 40 and prior was just under 80.
I also had a period of time where I had horrendous FPS. Pinging was well over 2000 to server but I found pinging anything was over 2000. I dealt with this for a time until I lost my connection entirely. This turned out to be a bad cablemodem\ router.
If it worked fine before then i suspect your CPU is overheating due to dust, especially if you have pets, you need to clean it often.