Precisely, Fribbles. When I played Enclave, the first thought I had was, what if they employed this simple mechanism of attack/defend into the multiplayer version of Dungeon Siege? It would have made the game much more engaging.
Also shambler, something you should know about Dungeon Siege coop: Its not the single player campaign coop. Its just that the multiplayer world is also a campaign. So you can play the one-character multiplayer campaign with other people, but you cant have two guys controlling a party, moving through the campaign story.
Also, for those that enjoyed Dungeon Siege coop, Ive been following the progress of the Shadows of Winter mod which looks to be a huge, professional overhaul of the system, with completely new monsters, an in-depth story and lots of other changes (most notably getting rid of the hack and slash gameplay). Since Dungeon Siege was pretty useless to me after I finished the SP campaign, Im hoping this mod will breath some new life into the game for me. For those interested, heres the URL:
http://dynamic4.gamespy.com/~shadowsofwinter/