I decided to do some poking around and see what threads there are about spectators and all I seemed to find was a bit of suggestions on how to make it better.
What I want to know is why with over 100 games up pretty much 24/7 (right now) there aren't any with spectator slots? My best guess is that there's a lot of paranoia about players not being able to join because in the bottom-right of a game lobby the "players" count currently includes spectators so you can have "10/10" players but you still need some more as you have some spectators. I suppose this is understandable since so few games have spectator slots so people aren't aware that in the gamelist it will say x/12 if you have two spectator slots.
One possible solution I can think of is having a couple spectator slots as a default and you can up it a bit if you like. I can understand how in DotA you wouldn't want to have spectators unless they're necessary as referees because it was player-to-player instead of player-to-server like HoN so the spectators could actually be helping with lag. But in HoN I don't see any real reason to not have spectators unless you're really nervous about people coming in with a friend who spectates and ghosts for them.