Great point.
I found the requirement of having to tie up 6 characters for 3 tasks annoying, but something else was bugging me about it and I think what you wrote was it. I still would have prefered 3 tasks for 3 characters and just make them longer though. The fact that my drop rate was horrendous and collection them tied up 6 characters for well over a week made it that much more frustrating.
Speaking of the number of characters, I think having 7 characters for what would probably be considered a second or third tier Disney movie was also a mistake. For this level of movie an in game, non event, content update would have been a much better choice. If they are going to continue having 7 characters for events than leave the events for movies that actually warrant having 7 characters and L&S isn’t one of them.
p.s. Please don’t take my comments about L&S as an attack on the movie, that wasn’t my intention, but with such a large selections of Disney movies their are far better choices they could have made for an event. If you enjoy L&S that's great, but I’d hope you’d agree that their are other more “deserving” movies.