But because of the addition of multiplayer, I was concerned about how mods will be shared now. The rep confirmed to me that players will be able to use the new multiplayer framework to find games incorporating mods but, better yet, all XP earned in these games will stay with your character. I was promised persistence across all games, be they mods or standard games.
One final interesting tidbit: all loot dropped in multiplayer games will be client specific. This means that the items you see in your game are only in your game. No need for mad dashes to grab all the high-level loot drops!