Originally Posted by Zloth
"a main storyline for solo players"
That's what killed Star Wars: Knights of the Old Republic for me. If you wanted to play with your friends you were relegated to a single, group dungeon and you wouldn't see a new one for another five levels or so. Basically, if you play with your friends then you have to repeat the same content a dozen times. (There were some "heroic" areas but those weren't all that big and seemed designed more for pick-up groups.)
After all those years in City of Heroes where I could play the storyline content with all my friends (whether higher or lower level), I'm really spoiled on this. I fear it may turn me off from MMOs completely.