I did every thing exactly like you stated and went from a 9/10 on the ipv6 site to a 10/10 but after a full reboot I'm still getting all the same error codes in D2. All other games and services work fine. I hope that Bungie can get a fix to it at some point soon. Thank you for this info in any case.
I forgot to mention I restarted my computer and manually disabled/re-read enabled my network adapter to make sure it put the changed into place, but I'd that's not working for others it might be some other issue causing the disconnecting
Whilst I guess if you are not playing D2 you have time to try things do not hold breath. This is not client side. This is very unlikely to be BT. This is not a major server down D2 side. This is routing of traffic from specific ISPs into D2 servers. This is DNS, or Load Balancing, firewalls, other security or network performance solutions, some dead hosts in a cluster, missing routes dropped due to table limits. Not something the user will fix. There has been a change Bungie infra side. It broke things because reasons Whatever it is, the length of time is really poor. I would be very concerned if I was managing the infra at time taken already without having at least been able to move traffic to alternate routes and/or viable assets.