It did feel a bit odd.

Did a rolling of 100 d20 now.
Slight disbalance with 28 rolls in the 1-5 range and 24 to each of the other three ranges. 
6 natural 1's. 8 natural 20's.

A second round gave a balance still in the lower sector, but not clearly biased yet.
27 1-5's
25 6-10's
21 11-15's
27 16-20's

4 1's, 6 20's