This is just an idea for upcoming tourneys to increase the number of participants. How about organising two tourneys? One as it is now...everyone can compete and one specially for beginning or just low level players to for example lvl 9 or 10 max. Or you can change in two different leagues: a first and a second division. You can promote from the second division to the first division by ending first or maybe the first two of a second division tourney. Same for the first division....the ones who ends last and second last are put in the second division. This way there's more a competitive mood in those tourneys and this may increase the number of player who will participate. A good idea will be to hold these tourneys at the same time to prevent player to win both with separate chars.
Just a thought!