I have browsed around this issue, I know its happened often in the past and the only other things that seem to cause it are in game overlays (i.e. Game Mode which you said you didnt have on) or overclocked cards (or bad updates/drivers). All of which seems silly, but thats FFXIV for you.

I installed that same update but can still play (Max settings) but I don't OC or use in game overlays (aside from Nvidia's on occasion)

Windows and FFXIV just never plays nice.... I'm sorry, I wish I could help more