First of all I think this page needs to be updated.
https://help.elderscrollsonline.com/#en/answer/30903
I play on PC-EU after u44 I noticed a serious deterioration in the connection especially during prime time.
Checking which IP addresses eso64 communicates with as it load different instances. I noticed that the path to reach the server can change substantially.
As limited as my knowledge is, it appears that Deutsche Telekom discriminates or throttle between connections on certain routes.
So what can I do to document this situation in a way that is useful to you?
Thanks