Crygil posted an important announcement last night concerning the lag and associated performance issues in Naxxramas. Blizzard has made some recent optimizations to Naxx, and they want to know what all of our experiences are like in the instance this week. As such, they're asking everyone to post feedback in terms of performance in the thread over on the official forums.
Now by performance I don't think they mean "My pocket Paladin can't tank."
What they're looking for are detailed reports such as "When I was attempting to do the Heigan dance, my entire group lagged behind a good 5 to 10 seconds. We decided to go and raid Hogger after we wiped for six hours in a row." Or "The Ice Block appeared after Frost Breath when my guild was taking down Sapphiron because of the 30 second lag."
Matt Rossi wrote a great piece yesterday on the need for designing the fights around latency. Hopefully this will become less of an issue as Blizzard works out their backend mechanics; and it appears this change is a major step forward.