Annoying lag increase when in an instance

While in any zone lag isn't too bad, I hover over the computer thing and it reads 63ms (which is insane and sure as hell does not feel that fast).

But as soon as I enter any instance it definitely feels like my lag has doubled. If I jump on my main, my characters don't jump until I've landed. Maneuvering melee characters is incredibly frustrating when this happens, and the mobs will reposition themselves a lot.

The stupid thing is my latency will still read 63ms! No idea what is going on, and I'm wondering if other people have noticed this happening to them when they enter an instance? I can run around Stormwind and IF no problem.

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

I have a similiar issue but its only some instances but it was only instance with large open area that I would lag in underbog, ramparts and Azjol-Nerub, it was so laggy in there for me that I didnt even bother with it.