humm... I think that's not possible. You all have too good connection to experiment REAL lag. I have, and I'm depressed.. hhahaha
Anyway, when It LAG, and I say LAG, i can move, in the map I've seen (anyway, there aren't monster at all, and no ally, aberything disappear), and when I reach black area, i don't go further. This is becouse the map is picked up piece by piece... Maybe you can change the client to download the entire dungeon at once (it will be laggi at first), you should find the function that download the piece of map.. I think...