I thought the problem may have been Radeon ReLive but it makes no difference if I disable that.
Exclusive fullscreen improved the fps to 20, but when windowed the recording came out at 8fps, both of which are unwatchable.
Here's a sample at 8fps windowed.
https://1drv.ms/v/s!AtfmJnucY63Bheh3SV_G5QbtVJ2Kew