This does sound very similar to what I’ve been going through, I have also had those disconnects on the login screen, I would have hoped several maintenances would have fixed it by now but it hasn’t and my tickets continue giving me the run around like it’s a me issue when it happened after a them issue and it just feels like it’s still lingering…but they don’t like to acknowledge stuff like this.
PS: it’s still occurring. My latency randomly spiked up to 800 while doing an old legion raid, solo, in the middle of the night, and stayed there for about 15 mins and during that time everything was lagging horribly, delays on spells, looting, visual mechanics then it went back to normal again during the run…I wonder if its instance based but as I stated in the initial post, i was haven’t it outdoors in Dornogal too /shrug