We both have similar windows computers and share the same internet so lag i feel he also does. We've been leveling another class and spamming dungeons so we've only been doing dungeons where we get lag noticeably. I can say when we were in a not populated city we were lagging as well so I don't think its just dungeons.

We usually play 6 pm central time to 11 pm tues-friday, on sunday and monday we play at any time of the day and still experienced the lag.