Well it is not. Not really. Look through the in-game system setting and check on game speed. When I was new I thought that I had a really slow connection at 512 kbps because I was lagging really bad. I checked every single in-game option and found out that the game speed affects it.
I found the game speed 8-10 is somewhat lag when there are so many people on the same map (skills take forever to cast, browsing through the BT takes 2 mins to load etc) yet walking seems to run smoothly
I tried game speed 1-5 and the same skills cast almost instantly on the same crowded map, yet the animation frames will be reduced dramatically. I believe game speed 4 is the best on a slow connection, because it has average animation frame rate, and almost no lag.
I hope this helped. please leave a comment or email me (e-address on the left<----)