Wowaddicts Legion

You have to kill a specific npc, he has 100% drop chance. And you have to be carefull that the npc which is helping you dont hit him more times that you so you can loot him.
https://www.wowhead.com/npc=86535/overseer-lykill

I know - I have killed that specific NPC over 5 times.

In the vicinity of the quest NPC there is already a quest NPC ( on top of the one that is with the player for the questline, ) & as a hybrid caster / melee class ( enhance shammy is silenced in melee range..

As such - it is not always possible to hit him more times than the NPC does, as the mob silences / immobilizes the player's toon… So as such - while WoWhead reports the drop rate as 100% - the mob wasn't even loot-able after 5 attempts of killing the boss.

well its 100% drop rate because I modifiqued it long time ago, the real trouble with it in your case is that npc is being who damages him more than 50% hp and so loot goes for npc instead of you…I will check it now but I recommend you to use your ranged spells from distance so you dont get feared or silenced. I think that even if you hit low with that spells it will get the job done. I will update you about it now when I check it. Regards
PD: Tested just now and it dropped in the first try. If you want, you contact me in discord and I can help you with it when you are online playing.

I did complete it; however the silencing mechanic of the fight seemed to be far moreso pronounced than my recollection of Legion content; the issue makes for enhancement shammies & likely other classes to barely be able to attack / properly attack / complete the quest unless one is hilariously over-geared ( Legionfall gear 850 iLevel with all weapon traits unlocked.. )

Nice you completed it, grats ^^. I will check and I will increment the time for applying that silent spell. Thanks you for your feedback ;)