Unable to solve severe Latency Problem

[Notion 0]

Hey guys,

I have severe latency problems when trying to connect to any WoW Server, including Nighthaven.

By severe I mean latencies from 600ms to 20 seconds. There are some moments (phases of about 2-4 seconds) during which the connection is alright.

All (!!!!) other applications and even pinging my own cmangos server via ping command returns very low pings (18 to 50ms).

The problem is probably not "server-side": All the servers I tried have fine connections with low ms to pretty much all other players.

Things I tried:

Using ExpressVPN: Because I assumed my provider would have a bias against wow. Didnt help though.

Reset Router: Check, nothing changed.

Resetting ipconfig and flushing DNS: Check, nothing changed.

Using Google for DNS: Check, nothing changed.

Rebooted Computer: Check, multiple times, nothing changed.

WinMTR: Nothing suspicious, pings and packet loss are quite low.

Tried to connect from another Machine using the same router via wlan as well: On the second machine, connecting to WoW works just alright, ping about 30.

Just reinstalled my network adapters. Nothing changed.

I can not really figure out what else to try. Any ideas? It seems to be some kind of problem regarding my system that has problems sustaining a stable connection with the given client.

I'm still hoping for a solution that does not involve reinstalling windows. Thanks if you want to offer any help.