Like most of the other players who have this issue, I've also had to go back to DX9. I hope that we'll see a fix of some sort down the line so we'll all be able to head back to DX11 and enjoy the prettier graphics. As an update, I found that this eventually happened to me in New Gridania, particularly while staying in The Roost for a certain amount of time. Considering the areas this happens at, I almost feel like the cause of this might be the reflections from the floors. All of my drivers are up to date, and I've also been through a complete reinstallation in the past just to see if it might have fixed the issue.