@Rok - Just played some more multi on BL2 today, and I think the hosting is done client side. If the host leaves prematurely, then all party members are booted out of the game. I can't confirm 100%, but I'm leaning towards client side hosting like Borderlands 1.
@OpusMaximus - Sent you a Steam friend invite. My ID is JeanH13, or you can go here: http://steamcommunity.com/id/jeanh13