It’s announced to work with multi player, so I trust they are working on it:
More players, more glory
Launch epic multiplayer battles of up to 8 players, then build your own maps using the map editor. Fight across swamps, icy fields, summer plains, and even the wastes of Outland!
But Diablo 1 have the same problem, multiplayer doesn’t work, it seems the backend isn’t set up yet?