Someone said it on read it and I'm going to say it here:
How did they expect people to NOT join together and zerg though enemies?
We do it in FATEs.
We do it in A-and-S-Ranked hunts.
We do it in 24-people raids.
We can even go into Diadem in a 24-people alliances via FC airships!
Don't punish the players because you though we wouldn't do what we normally do.