It doesn’t seem to be in the base Rarity. There’s a wowhead comment regarding tracking it from some known mobs, but it’s known to be short on count since the item appears to be a world drop.
What I’d like to do is test some areas out to figure where I can maximize kills/hour. Tracking in Naxx is no issue; Plague Quarter is 92 mobs, I can clear it it under 2 minutes, should get close to 2500/kills per hour if I can throw enough alts at it.
But I can’t track kills in Ulduar for some reason - I’d really like to know if Conservatory of Life is even more efficient. But using Ulduar isn’t working. Neither does zone ID #4273 as per wowhead.
And for those here to tell me this is a terrible idea - I’m well aware of that, but the goal is a completed toybox, and well, if I had literally anything else I could go for instead, I would.