Quest Issue: Unholy Coldstone Not Itemized?

[Mingo]

Failing to complete the bronze shackle quest because despite long efforts the "a goblin priest" in Permafrost Keep does not seem to be dropping the Unholy Coldstone. Killed 50+ of these creatures today w/o them yielding their quest drop.

On live it was not this rare, all of the foraged drops and other drops are IG, is there a reason this item is missing. Literally 3+ hours smashing most of the goblin spawns in zone w/o this quest item turning up, is it possible it's set to be too rare?