While I agree this should be addressed, it´s not a bug or an exploit. Morkuldin and Blastbones are considered to be NPC´s. All NPC´s in the game can apply a snare called "Hamstrung". Hamstrung will apply when:

* You´re attack from behind or from the side
* When you´re attacked while sprinting (regardless of where it hits your character).
(these findings are purely made from my own testings, so can´t say if there´re other ways to trigger it)

Hamstrung should be straight up removed from the game as a debuff if you ask me. It serves no real purpose, neither in overland PvE (where you´re more likely to fight NPC`s) or in PvP where it´s a lot more abusive.