Why is a character's skill rating variable in DnD while defense (aka armor class) is static? Characters use their skills to overcome events and challenges, and they use AC to overcome attacks. When a character is attacked the attack itself is variable. It may or may not overcome the character's defense (AC). Yet when the character needs to overcome some issue through the usage of a skill the external event is static, a fixed DC by the DM, while the odds of solving vary, and boy do they vary!
Shouldn't we look at DC as a center point for difficulty and the die roll simply represent a variation on the difficulty. For example a lock may be tough (DC 15), but given a situation the event may be a bit less hard (low die roll) without become average (DC 10) or a bit harder (high die roll) without becoming challenging (DC 20). What is fixed is the character's skill. So the problem either falls below the character's capacity to solve it through a skill check or it does not.
So a character with a skill of 14 would be below average at solving a problem with a "though" rating (DC 15), but a low roll on behalf of the GM would indicate the DC is actually 13 (slightly less hard). Given that value the character successfully solves the problem.
A static skill value and a variable DC makes more sense to me than a fixed DC and a roll that affects skill. I've always been troubled by the issue of my character's unpredictability when resolving a skill check. Will he fumble it or will he succeed. In my mind it sounds better if my character fails because the problem was surprisingly hard rather than my character being sporadically stupid.
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