hmmm...that's really weird. Your card does support dx12 and you are already on it (as DXdiag says you are). Well, you can try a clean install of the latest build and see if that fixes anything. Also you can try the stable version, and see if that one also crashes in dx12. And lastly, you can try the recent released vulkan backend and see if that works for you (buid 748 and up I believe). Sorry I couldn't be of more help.
Running Dolphin in my super NOT powerful AMD APU 7410 w/R5 Graphics (Integrated), 8Gb RAM
Dx11 Backend
Native Resolution, Ratio: Auto
Everything else is on Default
Dx11 Backend
Native Resolution, Ratio: Auto
Everything else is on Default