Out of curiosity, is this something that could simply be turned on at all times, similar to how ranging over a map is always pseudo-random with the Go toolchain? Assuming that the cost is negligible, it could be a net win.
I took a look at randomizeScheduler. I think the only noticeable cost would be an additional loop in runqputslow, which is called to move half of a local run queue to the global queue. That additional loop will be over the goroutines being moved to the global queue. Currently I think it can be up to 128 entries. Since runqputslow is only called when the local run queue is full, this isn't going to be particularly common. There would also be a bunch more calls to fastrand.
So while of course someone would have to benchmark this, it seems plausible that the cost would be fairly low.