Vilebranch trolls live primarily in the eastern section of The Hinterlands. Like the Witherbark, they battle against the Revantusk trolls, mainly because the Vilebranch wish to use the smaller tribes of the Revantusk as sacrifices to Hakkar the Soulflayer. They are almost exclusively found in Jintha'Alor and the Temple of Zul.
The word 'headhunter' is typically used to denote a person or tribe of persons who kill hostile (and sometimes benign) intruders, and take trophies - typically, the head of the slaughtered intruder. Given the known traits of the troll tribes listed above (such as cannibalism), the class 'headhunter' seems grimly appropriate.