Hello friend. I have been having this problem as well and it drove me nuts. Apparently the crash happens because there is not enough power getting to the card when FFXIV tries to run on DX11, I solved it by adjusting the voltage of my card in BIOS to 1000+, but you could do the same using MSI Afterburner.

Anyway, hope that you've solved it already, and if not, that this helps.