A simple SOLO spot for just grinding kills from 0 to 100%:
This is for those of you who, like me, don't feel like messing around with all of the other various ways to raise your completion bar (picking up ammo, doing things with said ammo, iron stars, etc.)
The non-elite Iron Laborers that are found all over the pit each count for about 1% per kill. However, most of the time they have an elite that patrols around them. The area I'm posting about has MANY Iron Laborers with NO elite patrol; and they respawn very, very quickly.
Coordinates are around 48, 23. I will post a picture of the area on the map as well as a detailed photo of the spot I'm talking about.
http://i.imgur.com/jaMGIMs.jpg
http://i.imgur.com/Sc4t4fl.jpg
2 things to keep in mind: Unless you have invisibility potions or spells, you may need to suicide yourself once to get down here initially (I found this spot by accident after falling off a nearby cliff). Once you get there, the orcs are very easy to kill and you should be able to hit 100% and hearth out in no time (depending on how many mobs your character is able to handle at once, of course).
The other thing is that while there is no elite patrol near these mobs, there ARE elites "nearby", so just be mindful of your surroundings and try to always pull out of the way to the main corner (see second posted image for clarification).