The heroic encounters in the River District are a funny thing. There are four large ones in total - three that share a spawn timer and appear in one of three corners of the map (I don't know if their order is fixed or randomised), and one that can be triggered by player hand-ins and is located almost right next to the zone's base.
As a result, everyone runs the latter all the time and general chat is flooded with invite requests so that people can chain-run the encounter by quickly hopping from one instance to the next. Meanwhile, the other three events largely go ignored. (The fact that the teleporting mobs that are part of Gyrion's forces are super annoying doesn't help.)
MMO min-maxing at its finest.