Yeah, I got tired of that shit too. If the other players don't catch up to me after I kill the first wave after entering the dark zone, I will check the roster. If I see that there's 3 players in the fireteam and I can only see one other player on my radar, I go to orbit and try again. What I've been seeing a lot lately is that sometimes one player will immediately depart and they'll only be me and one other guy. But when we get to the final boss or if the boss only has a sliver of health left, matchmaking adds a 3rd player. It's not the guy's fault that the system added him/her to the strike so late, but it still irks me.

exactly

See it happen all the time. Same scenario as well