I have the same problem, and have tried your troubleshooting steps. Here is my hardware info, and attached is my DxDiag.txt.
Radeon Software Version - 16.2.1
Radeon Software Edition - Crimson
Windows Version - Windows 10
System Memory - 16 GB
CPU Type - Intel(R) Core(TM) i5-4690K CPU @ 3.50GHz
Graphics Card Manufacturer - Powered by AMD
Graphics Chipset - AMD Radeon HD 6900 Series
Device ID - 6719
Vendor ID - 1002
SubSystem ID - 2010
SubSystem Vendor ID - 1787
Revision ID - 00
Bus Type - PCI Express 2.0
Current Bus Settings - PCI Express 2.0 x16
BIOS Version - 013.010.000.007
BIOS Part Number - 113-SS2G02-002
BIOS Date - 2011/03/30 21:29
Memory Size - 2048 MB
Memory Type - GDDR5
Memory Clock - 1280 MHz
Core Clock - 840 MHz
Total Memory Bandwidth - 163 GByte/s
2D Driver File Path - /REGISTRY/MACHINE/SYSTEM/ControlSet001/Control/Class/{4d36e968-e325-11ce-bfc1-08002be10318}/0000