These are..way too common.
I think they're meant to be a rare drop from the elite/named NPC loot table but it seems somehow they are in the Tenement Orcs Loot table because you seem to get one from that quest nearly every time its run.
Would we be able to take a look at that and maybe reduce its rates from that specific quest?
They seem to be dropping from mobs above a certain HD class.
its because every dweeb/bandit/thug type NPC can drop these.