Found a solution to the black screen, ffxiv_dx11.exe related black screen I was having. Since I'm running the game on GNULinux with WINE what worked for me may not work for you. But might at least give you something to try or a new direction to search in.

Everything is in an earlier posting in this thread., post #14

not sure if a pasted link will work but try this.

https://forum.square-enix.com/ffxiv/...=1#post6504473

Hope this helps. Good luck.