My first time in the Strike in the PC Beta, I was matched in right at the end. While I've played it before, I can only imagine how disheartening that would be to a player who is playing it for the first time. They're missing so much. Edit: To be clear, I mean just the first time. So, having some kind of permission in place so that players only can be matched in progress after finishing the Strike for their first time.
Definately a good idea, and surely it would be easy for them to implement. They are already keeping track of what missions, etc that you have completed. So during the matchmaking setup (evaluating guardians) it would just check the database to see if you completed it, and if not, load into a fresh match, otherwise - take best match. if strikeXYZ != complete: loadstrike(freshmatch) else: loadstrike(bestmatch)