Beware if you use Avast 2015: System Gets Borked After Optional Update KB3000850

Question

I did controlled testing with Windows 8.1 x64 Enterprise test system.  In this case, I installed optional update KB3000850 in a perfectly working and well tuned setup that was already running the up-to-date Avast 2015 Free antivirus package. 
The update went in fine, but basically the system was badly broken after the update, emitting things like:
...and this one during logoff or restart:
Worst of all, the system would not successfully reboot.
A look at the Avast forum reveals that a lot of people are seeing these issues.
In order to successfully install the optional KB3000850 update and have a working system,
BEFORE DOING THE UPDATE you should remove Avast antivirus completely
using the AvastClear tool: 
http://www.avast.com/en-us/uninstall-utility
Some have reported their systems continue to work after the update and after reinstalling Avast, but in my testing my test system was re-borked in exactly the same ways by doing so.  Then the problems were again corrected by removing Avast.
For the moment I've put my sysetms back on Windows Defender, and everything seems to be working fine with KB3000850 in.
Avast engineering has yet to comment.  I'm sure they're scrambling to find the problems.
-Noel
Detailed how-to in my eBooks:  
Configure The Windows 7 "To Work" Options
Configure The Windows 8 "To Work" Options

Answer 1

No fix has yet been posted by Avast (clearly they want to test it thoroughly), but reflection on this update yields some poignant questions about just who's at fault here...
1.  Did Microsoft do in-depth testing of KB3000850 on systems with 3rd party antivirus software installed before rolling out this update?
2.  Assuming the answer to the above is "no" or "not much", aren't Microsoft's managers sensitive to the fact that Windows Updates are losing credibility?  Hint: 
Making an update "optional" doesn't absolve Microsoft from one bit of the responsibility for making it work right.
3.  Did Microsoft make early copies of this update available to their partners?  For example Avast?  If not, why not?  Their user base is in the hundreds of millions.  If for no reason other than self-preservation,
does Microsoft not think it's important that their updates not break actual systems in the field?
4.  For what it's worth, I've had zero problems with the update after removing Avast completely and dropping back to the integrated Windows Defender.  Is this Microsoft's plan?  To eliminate 3rd party antivirus vendors? 
-Noel
Detailed how-to in my eBooks:  
Configure The Windows 7 "To Work" Options
Configure The Windows 8 "To Work" Options