The thing is, I've been on both ends of that, if it's somebody on my friends list who pops in late, it doesn't bother me one bit. If I'm doing the mission, I would have done it anyway, so why would I be bothered? What goes around comes around. Yesterday a friend dragged me through the nightfall even though he had done it already so that I could get loot...
And, again and again and again with this, IT'S RNG!!! you getting the legendary doesn't take away or add chance for the others to get it. Being passed off at you for that is just stupid.
Yeah I usually Dont get upset when people jump in either. Needless to say I'm not friends with that guy anymore but I did get an invite from the other guy in the party lol.