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.
This cuts both ways. Just played the strike again and both players bailed and I was solo for a bit until two new players eventually joined. You gotta fill out those in progress strikes/matches first and foremost. I do agree it sucks to be a newbie and get tossed right into a boss though. Then again it's not the worst thing when farming lol.