It isn't bizarre. Within a limited sample of rolls you might get strings of lucky or unlucky numbers. (This is what karmic dice is designed to prevent, as strings of failures can be frustrating.)
Roll 100 times, record the rolls, and then plot them out in a histogram. They should be roughly evenly distributed from 1-20. I highly doubt that Larian somehow messed up randomly rolling a d20. The only thing that might change this is if karmic dice is on.
