Given the recent power increase to the nightrisen, it might be reasonable to return the "Bone Knuckle" drop to them. Make it unsellable to prevent exploits and our alchemists shall once more be delighted to mess with the dangerous negative energy alchemy.
There's other ways to achieve the negative alchemy theme. I find knuckles and orc teeth to be silly drops that mainly just contribute towards the lag of the server.
Lag? Lag is non-existent and only occurs in big server events.
Just keep resets once every 24 hours and it shouldn't be a problem.
Agree, i only know of one low level quest where you can get hold of them. Maybe just give them a low drop rate like 10% so only dedicated people will bother hunting nightrisers for them.
EDIT: Or make them drop only on the more powerful nightrisers i.e. Commanders/elites/high warlocks/marksmen