I think more people will flock to HM, once single player type games are implemented, I know there have been a few times people log on and no one else is there. Also, it seems every few weeks a new group of players show up and the old group dissappeares.
I agree that some type of single player mode would help community grow. When you log on and noone else is in the lobby there is really nothing to do while you wait for another player.