Students and low experience pilots flying Xcountry circuits must happen because their instructors taught them. Do instructors feel this makes sense and is it part of their training/approval ?
Re faster traffic catching slower ones up in the circuit - I am always amazed when pilots of say an Arrow can't slow up to sub 100 on downwind when they can see traffic ahead. Perhaps part of the transition training onto faster a/c should be flexible circuit speed management.
I know before anyone says it that by the time finals comes there are a/c with a higher approach speed that even vne of a microlight ahead but here it is probably down to the micro to keep its speed up on finals.
Never will be an easy answer but I am sure that wise and experienced instruction etc could overcome many problems.