There are a few other threads in here about really bad lag, causing the symptoms you describe. In all of those cases, there was a hop to "NTT" or something like that, Square Enix' ISP.
It started the week before the patch, which if memory serves me correctly, happens a lot before big patches, which clears up on patch day.
My experience was just that - it cleared up at patch day.

I think the majority of people (NOT ALL) that had posted on those three threads are either ok now or had switched to a VPN and were good.
I can't speak for everyone (obviously you are having this problem) but those threads which were on the top of the board have not sunk down to third page. One of them is still up her on the first page.

I know this doesn't help you in particular, I wish I had something more constructive to add (although one VPN, kill ping is tailored do find the best path and MANY people on that thread said it worked wonders Couldn't hurt to try the free trial. https://www.killping.com/)

GOOD LUCK! Hope you find a solution and some peace.