A quirk of relying on a twenty-sided dice for the outcome of most actions in a game system is equal chances of a 1 or a 20 or anything between. There is no bell curve. Even the most expert of heroes has equal chances of critting as fumbling. This leads to the syndrome of the lucky amateur and clumsy expert, where the character’s skill is often irrelevant compared to the roll of the die. Often at the most comedic of times.

This problem has been exasperated in most versions of D&D, which rely on ability checks, where the difference between natural talent and clumsiness is four or five points, roughly 20-25% leaving quite a bit of swing for the dice.