The lag is very real and it started when the two remaining clusters were merged.
Perhaps I can provide you a unique perspective:
I'm currently doing volunteer work in the middle of no where extreme eastern Europe (if you can even call Georgia eastern Europe

) and access the internet through a third world country's cell phone network.
Before the merger, the lag was in the 1,5-2 sec range , but since the merger lag has been a steady 3-5 seconds during Western European prime time in all zones. I also play US prime time, which is early morning for over here, and find the lag to be a steady 2-4 seconds.
Something has really changed since the merger and it really appears to by on Mythic's end. During the high lag periods, I can quickly load webpages and stream videos, which indicates the problem is not on this third world country's cell phone internet access system. If I can quickly load Youtube on a mountain village in the middle of no where Eurasia (seriously - there are cows and goats in the yard...), you can rest assured that recent latency problems are not on your internet service providers' end.
I am not a computer or network expert, but the nature of the delays indicates that Bioware pushed all of the new players onto Ywain's original servers without compensating for the extra use. This supposition is also consistent with their downgrade of the old Camelot Herald to a simple blog website that you could host for free on www.blogspot.com. The old Camelot Herald had many of other features - like the housing lot openings and realm war updates - that certainly required extra servers interact with the game servers.
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