I decided to update my BIOS two days ago, which didn't went fine, because I had to re-install Win 10. But now I have an updated BIOS and a freshly installed Win10 atleast.

I can't find the FF14 launcher, I don't think I have it anymore. But I can start FF14 from steam, which I usually do.
Do you recommend i reinstall FF14?

Anyway I haven't got any DirectX 11 11000002 error since. I have monitored the GPU and I can see that the D3D Usage have gone up to 100% without triggering a DirectX 11 error.