I was able to roll back the regressions by rolling back Xorg and Mesa. Xorg was the worst offender, in Mesa only the hyper-Z issue caused a slowdown but Scorched3d locks up on the HD6750 if you use hyper-Z with Mesa 10.2. Works fine with Mesa 10.1, and both work fine with hyper-Z on the Radeon HD5570.
I first installed the 3.14 kernels after this point, at first could not use them because of a GPU power management firmware bug. Last week a new Lnux-firmware package fixed that, and I found no performance regressions between the 3.13 and 3.14 kernels on my systems with the use cases I have. All the problems were in Mesa and X.