Although I seem to have no problem with lag anywhere I go, the only issue is when I'm trying to go from Opal to Obsidia and back. It only occurs in the specific line that acts as the border. This might be where the connection is, or just that many events are presented simultaneously (I don't know), but I don't have the problem anywhere else. Even in the old maps where no checkpoint was between Obsidia and Coral or Tanzan area and Chrysolia.
I know it reduces lag, but I enjoy roaming around the region more without many checkpoints.