A long long ago, there was no divisions and long challenges (actually all cc contests) were combined. it was fun having many 3 stars beating a 7 stars!
In long challenges we usually prepare 11 problems, and choose the 8 easiest for div2 and 8 hardest for div1. However I noticed that some 4stars struggle in the first problem of div 1 (actually last time one 5 stars got many WAs in my cakewalk!).
So I was considering to share one or two problems between divisions. Div1 could get 10 or 9 problems. If the problem is not immediatly trivial, I think most 6 and 7stars coders will not care too much. Moreover if we go berserk, we can combine both rounds and forget about divisions!
In short contest there are less time, so I think is fine to not share problems, but in long challenges there is plenty of time, and the shared problems does not consume too much time.