With SteamVR (HTC Vive) How much of the CPU is "supposed" to be taken up by vr.WaitForGPU?

I’m at about 50%, is that bad? What exactly does that mean?

That’s VSync. Your editor is probably running at ~180FPS, but the refresh rate of Oculus and Vive are 90Hz, so the CPU is waiting for the device to be ready before drawing anything onscreen.

Also if your pegging the GPU the CPU will need to wait for it to finish. Profile the GPU if your above 11ms you need to optimize or render less.

This may be related to this issue instead.