- I killed Xu'ba the Bone Collector the third time, and he's still not counted towards the criteria of achievements
- Gwugnug the Cursed seems to be bugged, as I killed him but no credit to the achievement
We have received multiple reports of this issue and can confirm it is not working as intended.
Other players have been able to complete the achievement correctly by obtaining the Heart of Azeroth neck, equipping it, and then killing the rare mobs again.
We apologize for any inconvenience while our developers work as quickly as possible to resolve the issue.