These little guys are all over the eastern side of the map in Neverdeath, which is a map you hit around the 25-30 level (depending on your gameplay focus).
Your first few missions in this area are the western side (graveyard side), but then a lot of your missions (particularly repeatable ones) will be on the eastern side.
Essentially - once you come through the World Travel gate, turn left and head towards "Craftsman's Rest". There are a bunch of little guys with very high voices that will squeal "Attack!" or "Die!" Many of them are hurlers. They seems to be a pinkish red with bluish armour on. When I say little, I mean they're the smallest looking enemies amidst the big guys that they like to hang with. They also like to attack in groups, making it quite easy to farm the kills if you feel you need to.
*** Spoiler - click to reveal ***I'm not sure if it's quite spoiler material or not, but they're on the way to the Charthraxis dragon fight. Tons of them all over the place before you head up the final set of stairs to where 'big green' is hanging out.
You will probably get this one naturally over the course of playing, as many missions will take you through the same area quite frequently.
If I knew how to embed a small picture of one, I would. If anyone else knows how, just let me know, and I'll edit to include a picture.