http://guides.gamepressure.com/divinityiiegodraconis/guide.asp?ID=8322 sounded interesting, but I didn't recall seeing it as I played.
I did finally compare the formulas and Butcher seems to be the current name, but the details are different. Butcher reads like it'll help out if you do get a critcal, but Hatemonger reads like criticals will come up more often.
So right near the end of the game I added Butcher 10 to my bow just in case, but I don't know if it came into play. I had been seeing as much as 10,000 hitpoints from one Exploding Arrow but they weren't all that common.
Did someone decide 'Hatemonger' was bad for business or something?...