1. That's a bug fix. People like me didn't like that since FW 10.4 the clock revved up to max speeds while idle since it increased temps unnecessarily. It is working like it used to, but it leaves a glitch with XF owners that they need to address.
2. The MLAA mode only supports 6xxx cards in official drivers. The unofficial drivers (hotfixes) have it working for non 6xxx cards, and perhaps it'll be added to official drivers one day.
All the drivers pre-10.11 have idle clocks at 400/1125 for me with 2 screens. 3D clocks are 860/1125. How is it a bug fix if it causes screen corruption on the desktop? It's actually introducing a bug - can't really use my desktop with all the weird stuff happening... If I unplug one screen, then the problem is gone (obviously). Not really a solution either, is it now?
And the lack of MLAA killed it for me pretty much. Good thing there's nothing wrong with 10.10e!
EDIT: The usual behavior for me using 10.10e and older drivers is:
2D idle + 1 screen -> 157 / 300
2D idle + 2 screens -> 400 / 1125
UVD mode -> 400 / 900 (causes a small flicker/tear when switching on/off - due to memory clocks/voltage changing, no biggie)
3D mode -> 860 / 1125
With 10.12s:
2D idle + 1 screen -> 157 / 300
2D idle + 2 screens -> 157 / 300 (desktop unusable) or 400 / 1125 (no problems then) + flicker/tear when switching...
UVD mode -> 400 / 900 (same as above)
3D mode -> 860 / 1125
EDIT2: And I hope AMD doesn't start to differentiate even more aggressively ... since MLAA is working great on my HD5850. "We decided do disable DX11 support on HD58xx and lower cards, HD6xxx and higher are better suited for it" or some other nonsense...