Diablo II specifically includes design elements to be playable via 56k dialup.

1) Latency hiding. The results of actions are determined ahead of time. The hit chance and damage value for melee swings and missile shots (arrows, spell effects) are calculated when you start a weapon swing or bow fire or spellcasting action. The duration of the action hides the network lag; by the time your sword finishes swinging, the packet describing the results has arrived.

2) Low bandwidth. The client does a lot of autonomous prediction and extrapolation. The server typically sends updates of monster positions at intervals of several seconds, rather than every frame. This can create situations where your attacks seem to automatically miss because the monster you think you're attacking isn't where your client thinks it is. But better to have that "lag haze" than to not be playable at all for lack of bandwidth.

This was all implemented for Diablo II after learning from the first Diablo.

Yeah, I played on a 28.8 modem. What he's describing is probably the result of someone using a "trainer"/cheat software that would essentially packet-flood the other player(s) so you can kill them and take all their stuff while they cannot respond/escape. Happened all the time once those hacks became prevalent, kinda ruined the [public multiplayer aspect of the] game IMO :(