I began getting this error on EXITING THE GAME only a few days prior to DF prepatch.
Attempted Corrections:
Clean install of new video drivers
Disable all addons
Removed Interface, WTF and Cache folders
Uninstalled wow, reinstalled wow
Attempted to set to direct x 11, caused full in game crash.
Force run Bliz app/game as administrator.
System is not overheating
Please help
Hello Tèren pls check this link maybe is help u solve your problem
if not is not i send other similar post but on windows 7 check this
Ya that was the fix for now. I went directx 11 and the crash is gone. I did run the DSIM repair, no errors found.
So something with my D3D12Core.dll is hosed apparently. However, it only started a few days prior to the patch which indicates it was something bliz changed. Not sure what to really do about it beyond hang at directx 11 for now.
Sad I have a huge new gaming computer.
SOLVED
I am running ASUS. The GPU TweekIII program that comes with asus is using that DLL.
I uninstalled GPU TweekIII, re-enabled Directx 12 and the crashes are gone.
It appears this is an ASUS related issue.
To check if any other program is using D3D12core.dll …
Command prompt as Admin tasklist /m d3d12core.dll
Nothing should be using it. If it is, get rid of that program if possible.
sorry Tèren i was not helpful for your problem and im glad your problem fix Thank you for solution 
Thank you so much for trying. It was definitely a weird one!
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