The reductionizer is pretty rare. I've only seen it drop once. But I've only done the Mech Guardian about 50 times give or take. Still enough times that only seeing one drop makes me think it's pretty rare. The earring too I've heard it taking close to 50 clearings to get, but on the other hand, you hear of people getting it in a only a few clearings, so maybe just uncommon on it.
Of course, I've spent many hours working on the wand before getting the reductionizer (at least 40hrs), and all I got was the cloak if I got anything. My luck is not always the greatest though. As examples, took about 6 yrs to get the dusty soriz pouch to drop for me, though I seen lots of other people get it, while I was waiting for them to leave to take over the camp, and of course, the one day, I got three 0s out of a 1000 randoms in the same day on raid loot. Luckily, one was a winner as there were no other rolls.