I think one problem is that there are an awful lot of people that have marshalled all or nearly all the legs.
One field yesterday had one of the guys who had never marshalled before and plays for a div 4 team. This bloke spent every game i saw running all over the field to make calls whilst others I have seen on fields many times this series sit there and do nothing! Is it possible that the individual is bored to death of the long day, the stress of dealing with us lot of moaning gits (lets face it we are on the field), for very little in return. I know I would!
Sam I agree with your points entirely, however I don't think the series is big enough in attendance to be marshalled by div 1 and 2 teams alone. Maybe 2 div 1 teams, 2 div 2 teams and 1 div 3 team (the div 1 team split up across the 4 fields to gain experience as Ian mentioned). However this still leaves us short. I think the average number of teams in div 1 and 2 is 8, which is only enough to cover 4 legs of the series. You may be able to cover one more leg with teams that only play one or two legs but there is still a short fall.
Unfortunately I don't have an answer to this, just posing questions. To me it seems like a catch 24, Sam you are right better marshalling will bring in more teams, as this is the key let down at the moment, but until we have more teams there are not enough marshalls to go round....