Seeming as we are in that waiting time again for another mmo to POP up I would like to spend time playing other coop games apart from minecraft. Don't point out the obvious ones like wow etc but decent 2-8 player coop games that can be played amongst guildies. I'll make a list of all that you suggest.
Gotta throw Sanctum out there, I honestly had fun while I played it but the real reason is I have friends that worked on the development. If you like tower defense then you really should try it though, best played in co-op.
NWN 2 is good, but you have to realize it may go a bit slow. But if you like that sorta thing, I guess even HOMM 3 is good.