I'm getting the same error. Screen flickering periodically, especially when not in a duty, leading to an eventual crash and a "application ffxiv_dx11.exe has been blocked from accessing Graphics hardware".
Sometimes I play several days with 0 crashes, other days it crashes 3-4 times.

This is the only game I play that I have issues with, many other more graphically intensive games run with absolutely no issues, so something with FFXIV is borked.