The story doesn't explicitly require the event, but I wasn't able to get to Arah. The giant doorway and path were all closed off. I'd read that the event is the key to opening up the door and path to getting there. Later last night, the door and path were open, but I don't know why. I was able to run from the Anchorage waypoint over to the Arah waypoint. The event still said "The Gates of Arah are under Pact control", but now that I have access to the Arah waypoint, that status seems less mocking.
