Mythic uniques and individual droprate.. wierd occurance

Hi,
So my last 4 Mythic unique drops have all been Nasekem the herald:
so about 1/50 for a mythic to drop, 12 mythics = 1/600 for a specific mythic to drop.
This occuring 4 times in a row is 1/600 * 1/600 * 1/600 * 1/600 = 1/129 600 000 000.
Soo yeah or something might be off in the code or my math wrong… but anyways, anyone else with this experience?