You are all missing the most important thing that differentiate solo vs group play.
Group play equate group drama.
Solo play equate solo drama; wait what?
I've played MMO's since UO/Mankind, the only thing I can say is, group play when more than a few always end up in drama. Do I want drama? No, I'm here to enjoy myself not to manage adult babies and their egos.
I so choose solo play, with a few friends here and there.