Help a noobie understand critical hits

[whswhs]

I prefer not to roll 84 dice; it changes the statistical pattern. If you roll 6d, the standard deviation is 4.18 (so two-thirds of the rolls are between 16.82 and 25.18). If you multiply by 14, the standard deviation is 58.12. But if you roll 84d, the standard deviation is only 15.65. So that central range is 235.88-352.12 in the first case, but 278.35-309.65 in the second. In other words, rolling more dice makes the outcome substantially less random.