Same issues here, game was fine, no latency at all, after the last maintenance/patch i am getting a lot of lag and disconnection issues when I didn't previously.

I have noticed that it wont happen if i plug in via wired connection instead of wireless. Though my wireless connection is over the 5ghz band and is at a steady 30mbs and works fantastic with every other game I play, its only XIV that is now having issues with my wireless connection, and I cannot figure out why, as it didn't have issues in the past. Issues only started up in the last few days after a couple months of playing fine. My hardware hasn't changed and I get no other problems with any other programs.