Regarding needing to team up at the top levels: I have played days and days and years of WoW, way back before the expansions, and I only have one near-top level character. There are so many ways to play each class, the replay value is IMMENSE and I keep going back to try new ones :) PvE server recommended.

Guild Wars is the other MMO in my top 3 with Lotro and WoW. Brilliant fun, very pretty, totally free once you've got the bundle (definitely get all the add-ons). Maaaaany hours on this one.