Here is the bug post I submitted. I am character limited, so I couldn't really say more than the following:
So, my Mythic raid team tonight was not able to raid at all due to an issue that was plaguing random groups of 1-4 players in our raid at any given time in Uldir.
Every time we'd enter, 1-4 players would have their latency spike to 1k+.
It was independent of ISP, even IP address. Would happen to different people as players entered and left the raid. Relogging would sometimes fix it, but just pass the latency issue to another player. Please fix this issue as its affecting progression.