I think I've run dry on EQ2. The game is "multiplayer", but I can't find any other players to play with. It's especially frustrating because I've run up against the solo/group barrier. All the interesting things to do require a group, but the things aren't interesting for the other people in the group with you. It's a similar problem I've seen in a lot of MMOs that put an emphasis on grouping for content that is only interesting the first time through. FFXI was riddled with quests and missions that you kept having to drag people back through if you actually wanted to complete the game's content.
MMOs need to focus their group-required content on things that remain interesting for the whole group. Raid content, where everyone gets some (or gets a chance at getting) interesting loot is one example. PVP is another example - Planetside stayed fun for ages doing the same sort of things with a very flexible group. Public Quests is another interesting idea but I've yet to see it implimented in a manner that remains interesting and active past the game's launch month. Ultimately the biggest problem with limiting content to group-only is that it forces players to find other players also interested in doing the same content. For whatever reason - the game is getting old, players have moved on to other things - when your calls for a group go unanswered, your interest in the game dries up rather quickly.