Eh, there have been instances on JP servers of players sniping the portals to BA, and one where an entire instance collectively refused to kill the outside NM to allow further progression inside BA (not Ovni but the other one that spawns where you need Feint L and Dispel L).
On Aether, when I've tried to do it there's been less players sniping portals and more instances just not being interested in going in. I did get in once last night, but only made it to the East/West boss rooms (and the other side failed to kill their add, causing us to wipe but it was still fun).