No evidence to proof the drop are controlled. However blizzard havent provide any evidence that they havent .
If random and probability is in such a way in D3. All gambling house will suffer heavy losses every year.
Blizzard's forumla have serious problem. It is very rare for a event happen and happen again some time or not happen in a long time in terms of statistic and probability.
Yes it is possible that you are the first or 500th but in probability but very very rare.