The original Neverwinter Nights was never a party-based game, and it was fan-tas-tic. One of the best RPG's ever, IMHO. NWN2, however, was a let-down. Dungeon Siege was ok, but in that game, the annoying thing was just that the party AI was so good. If you played it right, at some point your player character didn't need to do anything anymore except run somewhere and let his/her party do its job. That was boring. And to be honest, it wasn't really a sign that it was good, it was just that that game was so simple that there was never really any other choice. If you got a mage, it was always the same spell, got a healer, always the same spell, and everyone always had more than enough potions (whether it was mana or health) from autoloot to keep going forever. It was just dull. In fact, in the sequel they tried their best to avoid just that, because it had been the biggest complaint from their fanbase.
If you think Dungeon Siege was a good Party-based game and the NWN's aren't, then you just have to realize that you don't like party-based games. in Dungeon Siege, the party was a non-issue. It's only in games where parties start to matter, like the Baldur's Gate series and NWN2, that you can really enjoy them. (even though I didn't like NWN2 that much, but that was not because of the party, I loved that aspect of it)
