Not sure if this is a bug, before this is a boss area, this top part has a chest and you can get here on walking on the peoples huts.
But afterwards you can still get here, at north side jump on the rock in picture then to bottom left and you climb up.
I have to check if I can do this during the boss fight. that would be a easy ranged cheese 
However many bosses have cheesy high or out of range places where you can safely kill the boss with ranged, without them attacking back.
I had another one of these rock jump places in nameless pass but it was fixed with co-op patch. So perhaps if you decide to fix this one too, here you go:
