Most of you dudes seem to loiter on Reddit as well, but I figured I'd share this in case you missed it:
Easiest way to get your Husk of the Pit to max.
Load up The Wakening on Normal. Run past all the mobs until you come upon the room with the first Shrieker in it. Stay to the back and off the Shrieker, kill the exploding thralls, and dodge the Shrieker death bombs.
After you do this, stay in the room the Shrieker was in. 6 or 7 exploding thralls will charge you from the next room and then amble in slowly. Use your Husk to mow down one, and they will all pop and count as kills with the Husk.
They will respawn after 6 seconds and just keep coming over and over again. You can park here and shoot the slow walking exploding dudes at your leisure. Took me about 30 minutes to max mine out for Eris. Just don't go past the threshold of the door they come through to your room or they'll stop respawning.
did it in like 15 minutes just doing the regular old dark beyond. took i'd say about 380-420 kills.