I'm posting here because this was my first result when searching "XIV dx11 error". I'm not sure if this will fix it for everyone, but it has worked for me and my friend so far and we both had newer PCs with superior hardware.

BACKGROUND:

Out of nowhere I started getting "dx11 errors"
usually something like:
ffxiv_dx11.exe+3677EA etc, etc... a bunch of them, and the game booted me.
Anyway, I tried everything on every back page of Reddit and these forums. I emailed back and forth with Square. I reinstalled the game TWICE and even factory reset my PC. Still got the error. Then my friend told me about this fix that worked for them and I tried it and it worked for me too! I hope it helps someone else because I know how insanely frustrating this is.

FIX:

(do not have game running)
-Download Intel Extreme Tuning Utility
https://www.intel.com/content/www/us...intel-xtu.html
-Under Performance Core Ratio, set to 53x (this SHOULD be under-clocking your CPU. If it is over-clocking, only try this with extreme caution)
-Apply
THAT'S IT! Open up your game and hopefully this has fixed your issue. You will have to make sure this is running every time you play.

WHY DOES THIS WORK?

Not really sure. We figure not every CPU is fully tested for compatibility? 53x seems to be the magic number. I let Square know about it jic too.

****GOOD LUCK****