This memory is probably the strongest one in my WoW life. The day when I and a friend collected 20 people on lvl 10-15 for a raid in the five man instance Dead mines!
I have yet to solve the reason for WoW to remove that possibility and anyone else who remember these days? Shame one can't reach out to GhostCrawler and ask him why they removed the option to enter an instance with 40 people in a small instance such as Deadmines. They should reimplant it for all old instances up to Cataclysm content.
Oh, and hey, new to the forums. Didn't find anything in search option so...