Just thought I'd mention that 4.8-rc2 and 4.8-rc3 are still worse off than
before, even though both have changes for amdgpu power management (i.e., no fix
for this, and X still won't start any more, although I suppose maybe the later
is because I'd need a matching update to xf86-video-amdgpu I'm not aware of). 
I won't report any further lack of progress.