What cpu? Piledriver 8 core?
I had the exact same issue but I had also updated Advanced UI on the same day as the latest patch... Didn't take me long to find out it was the latest version of advanced UI causing the problem. You can read similar posts about advanced UI over on the site hosting that Addon. I rolled back to the previous version of advanced UI and the low frame rates disappeared.
My recommendation... Check your addons...