Same issue. Pre patch I had my normal crap lag, but it wasnt anything compared to now. Latency constantly 999+ when trying to do any kind of group content. Overland is pretty much same for me as pre patch where its not too bad. So just trials are mostly affected for me. Very unplayable. I had my team watch me kite blitz in first boss room of vet rockgrove, die because it didnt register that i dodged, then they saw my dead body skid across the room to where I dodged to on my end. Bar wont swap. Skills dont register. Theres an immense delay and desync for everything in group content. Its so unplayable I'm stuck doing overland stuff till this is fixed. Sent in a support ticket about it just to cover all areas in the case mine isnt related to other's lag. But I have a feeling its something to do with the update

Having massive spikes as well, sometimes to the point it disconnects me. Totally unplayable right now for me. Again before the last update is was pretty ok no real complaints or problems connection wise so it is not my end.

PC EU here

Those are good basic suggestions in the help doc, but as a long-time ESO player I have to say that the comments above are valid. Something is up with network stability in the game. Maybe it's patch-related, maybe it's more of an issue with the CDN/anti-cheat system... who knows. But the random lag spikes and de-syncs are real.

I use business-class ISP service; my traffic is given priority across the ISP's network as part of that service. It yields more consistent/stable ping times at least on that ISP's network. It's proven to be helpful when the ISP has congestion issues, so it's not likely to be an ISP issue. It seems more like something up with the game itself -- either the game's own network behavior, or the networking systems and servers it connects to.

I've had insane lag spikes as well and several times yesterday (9/4/21 and today 9/5/21) where the game instantly shut itself down with no ESO error screen popup. It closed as though it was just a browser window closing, no warning, no lag beforehand, and also while i was doing mundane things usually like looking through inventory.

Pre-patch, I hadn't had anything shut my game and launcher down instantly like that. Something is off with the servers because I've run multiple virus scans, checked my connections were good to my router, saw no issues with internet connectivity due to ISP; so my only conclusion is that it is ESO-specific.