I do experience this everytime I'm in an instance. Ramparts/Blood Furnace on both my DKs and Paladins have this issue. I've learned to work around it when using abilities and such but I don't know where the lag is coming from. I did the TCPAck change in the registry quite awhile ago and my latency is never above 70 on any of my 5 characters. Outside of any instance everything is perfect though. /shrug