DDO was the only real mmo that i felt had the community inherently built in, not to mention the flexibility in creating customized characters that doesn't have to fit into a particular role of dps, heal, tank or that a you need 1 tank 1 heal 2 dps to make a good group.
My opinion is that so long as quests don't stop being designed for groups, optional solo play should be fine. They only have a couple solo only quests in the game, thank goodness. Scaling is kind of anti-grouping at times (improperly challenging larger groups? who thought THAT was a good idea?) I preferred the old system of designed for 4. If me and a couple buddies were questing, so long as the other 3 pugs joining our group amounted to at least 1 competent player... easy peasy.