I sent an email to Jeniczek, but got no response, so I'll post here as well. Last week during our AQ40 raid, nearly half the raid group was experiencing an extended period of high latency (15,000 - 18,000 ms). It occurred at approximately 4am server time last Thursday, and lasted for 1-2 hours. During this time, it was completely unplayable for all those who were affected.
The curious thing is that a temporary fix was discovered. By deleting their WDB folder, and relogging, our players were able to reset their latency back to "good" levels for several minutes. However, after a few minutes, their latency would skyrocket back up into the 15,000 - 18,000 range.
During our raid last night, (approximately 3am this morning going off server time) we again had issues with a half-dozen or so players experiencing high latency. But this time, deleting their WDB folder had no affect. They were all NA players, from various parts of the USA, and have different ISP -- so it's not as if the issue is isolated to one specific region or ISP.
Figuring out what is causing these issues should be extremely high priority. It's incredibly demoralizing for our players to log on for a raid, only to suffer through hours of unplayable lag, while at the same time not have any issues on the other project. If it doesn't get fixed, there are a handful of people in my guild who I wouldn't be surprised to see quit soon out of frustration, because trying to raid with 10,000 ms each time just isn't fun...