It is also the closest waypoint to Nihlathak and, therefore, used for reaching him quickly too.
If you are farming Nihlathak (i.e. for his Key of Destruction), you can quickly and consistently find the exit to Nihlathak's Halls of Vaught by navigating the map in a clockwise Pattern roughly 90 to 135 degrees from the waypoint. For instance, if the waypoint appears in the west side of the map, the exit will always be on the northeastern side of the map.
Nightmare: 2 - 3
Hell: 6 - 7