The pseudo RNG in this game is random enough… Yes, there would be discernable patterns with a large enough sample size. You do realize a game like Diablo 3 that heavily relies on RNG would be impossible without pseudo randomness? Referencing true random sources such as signals from the cosmic background radiation or a nuclear decay hardware based RNG module is expensive, especially at the rate that this game cranks out random numbers.
People who don’t understand random, always bring up “Well, it’s only pseudo-random, herp derp” like that actually means anything.
Another thing about pseudoRNG is that the generation “seed” is based on the exact time the call for a random number is made… We’re talking down to microseconds. When the human element is introduced, it makes it more randomized… Sure, we humans can keep a steady beat, as there are many great drummers in the world, but even the best drummer is nowhere close to being atomic clock perfect… Well, except maybe for the late Neil Peart. 
Then there’s connection jitter, which also puts a degree of variability when the RNG call is made with a client-server setup. There are other variables that come into play, but human error and client-server ping jitter are the big ones.
Primals aren’t a problem if you do grifts per 1-1.30 min or if you make a lot of crafted items.
But yes, RNG or “RNG” sometimes makes you nervous and angry, especially if several failures occur in one game session ( for example, 3-4 bad ancient bracers out of 100, not a single Orek’ dream per 70 open&closed grifts, 2000 souls spent on recipe #2 and not a single acceptable amulet, etc.)