Circling back just ever so slightly to the RNG questions (while tapdancing around the drop rate statistical analysis dead horse), the kind of drop wierdness displayed in MMO's, and other types of simulations in general, has a great deal to do with ty KIND of RNG being used. Sure, you're pocket calculator might just have a random number button on it. But how good are those random numbers. Just how random are they?
The reason you see those kind of cyclical drops and why certain times of day are better for certain things in those instances is because of both the type of random number generating function that is used behind the scenes as well as the seeds used for them. If I use a standard system call for a random number (on a x86 chipset) and feed in the system clock time as the seed, there are only so many possibilities of the outcome. If I control all of the other variables, such as other processes running, network noise, etc., it is entirely possible to predict an outcome. That is because there are only so many discrete posibilities of "system clock" value that can be passed in as this seed. Can it be used as an exploit? Yes. That's why for items of higher security encryption, the seed when generating the encryption key is important.
So, that leads to a question: Toady, just how random is the RNG in DF? How robust are the seeds? Have you done, are you planning to do, would you consider outside auditing of the quality of the random numbers the RNG used in game produces?