Running with the Pack
It’s something of an extension of the mechanics of dynamic events and the player flocking that’s seen in the game. It does seem work well in Southsun given the difficulty of the karka. It seems like that large roaming pack is really what the zone was meant for, there was just previously no reason for players to form them.
This would work even better if we had a mechanic similar to the warbands seen in Warhammer Online (one of the few things that worked in that game), where one could freely join a large roaming zerg and see the other members of the warband. Only being able see your 4 group mates in the open-world is limiting.
I do suspect that the roaming packs will evaporate after the Living Story events move on. Unless ArenaNet has figured out a way to keep the zone rewarding, I would think player packs will migrate back to Orr.