The highlighted part is absolutely 100% false.
My first time doing this was with 2 people that had the quest, and 2 that didn't.
2nd time, I was the only one on the quest.
As long as 1 person has the quest, all they need is 3 other players.
Interesting, if you telling the truth, yet on the previous H4, All The Pieces/Dark Design, you have to have people exactly at that point... That I know as a FACT!
So, even if you can do Last Stand, you can't do All The Pieces/Dark Design... They will get to the platform and told " You are not eligible for this conversation". Oh, the other 2 guys that we joined up with, also tried to get their guild mates to help, they had the same result... If you know a trick I do not, please let us know.
All players must be at that point, you cant even be too far into it, like we all were, at the boss fight when they spammed for help, we had to reset the mission to complete that boss fight as a 4 man team.... That is just stupid or its bugged.
Yeah, my guild was not able to help out, so being in one, for these H4's, has no positive outcome, even though they did try to help.
The OP is still right...