Do not trust whatever humans have to say about probability in an immersed context in which they have an interest in the outcome. The fallacies are everywhere, even apparent paradoxes. Graduate students in statistics are easily stumped if you transpose the problem into a practical context. It's part of how our brain works. At the most general level, the problem here is the change in perspective that comes when you've gotten the first rush of upgrades. Considering this, the drop rates are in my opinion way too high. When starting the season, all of us had a workable build within the second night (on hardcore even, where you take things more slowly).
From the perspective of getting the rudimentary gear required to enable a build, i.e. all set pieces with any roll, the drop rates are such that it doesn't feel like an accomplishment but rather something you are entitled to upon reaching 70. From the perspective of getting that exact item you so desperately want, with the roll you require, after the rest of your gear is already in the 98th percentile of quality, they will always and necessarily feel hopelessly low. You're not getting anything else to comfort you while waiting either, since you've got all but that one thing. And so you will look for ways to better your odds, and suddenly some fool claiming that the ancient furnace will drop from a particular weapon rack on a particular night of the week will start to seem like something you shouldn't dismiss off hand.