What I was trying to get at in my first post is that the style of teaching is as important as the structure, that a small class is best made use of by an instructor who can amplify and steady and steer the students' enthusiasm. The big-numbers dojos that I have been in suffered not just from infrequency of direct contact with the instructor, but from the hierarchical attitudes and personal isolation that that context tends to favor.
An organization with a strong hiarchy should also be able to identify those who have teaching ability from those who don't right? A fair example of this is the US Military which in my experiance emphasizes teaching as an essential leadership skill very early in the soldier/sailor/airman/marine's career.
I know allot of senior sudents who are humble enough to know that while they can convey information... they are not the 'teaching" type.