Yeah pretty much the same results as me with my FX 8320, I'm guessing he has GPU accuracy on default or high, probably using Wii U Pro controller instead of the gamepad, and him being on a course with the MK8 AMD GPU-specific spectator bug (that hurts performance) isn't helping either.
He should do another video with gpu buffer cache on low, using the gamepad, and on a course without the spectator bug. (such as Thwomp Ruins, Cloudtop Cruise, SNS Rainbow Road, etc.)
Using the Pro Controller lowers performance?