For those who are having problems with DirectX Fatal Errors 11000002, here's a solution which worked for me from user Espionage724.

"I have a RX 580. Haven't had any crashing with FFXIV with the default DX11 renderer, but I use DXVK to translate to Vulkan, and this gives me better FPS overall (people normally cite DX11 having higher CPU overhead on AMD GPUs). For those affected by instability, I wonder if a potential solution to DX11 crashing could be to use Vulkan instead?

The short-version is to take the x64 (64-bit) versions of d3d11.dll and dxgi.dll from the latest DXVK archive, and place them in the SquareEnix\FINAL FANTASY XIV - A Realm Reborn\game folder (game, not boot). That's all there is to it.

DXVK is 3rd-party software, but as far as I'm aware, there's no known reports of actions against DXVK users from SQEX. It's used notably by people playing FFXIV on Linux, and I've personally used it for a few months now between Linux and Windows no problem."
Good things: improves performance, no crashes
Bad things: disables all overlays (like ACT, Discord, Steam), changes graphics a bit

Since this fix changes the default renderer from DirectX to Vulkan, it means this error is most certainly somewhere between Square Enix's side (in-game code) & DirectX and guys if you read it, add this as a data point in order to try to fix it.