Quest item doesn't drop

This quest item is not dropping: https://www.wowhead.com/wotlk/item=3...rithing-choker . Yes, I have already completed the quest in Drak'Tharon Keep with Drakuru and thus, Unliving Choker doesn't drop for me anymore. However, Writhing Choker, the quest item that drops if you have completed the quest chain ending in Drak'Tharon Keep is NOT dropping . I've sat in that god-forsaken place killing Withered trolls by making trains for 1 hour, I got 25% exp at level 77 and I still have not seen it. I don't know if the drop rate is 0.000000001% instead of 4% as said on wowhead or the entire alternative quest chain is simply not scripted, but here's my post about it .

Drop Chance: 4.13%

Writhing Choker and Unliving Choker will start different quests but lead to the same objective.
You can't even have both at the same time.