5e (and lots of other swell systems) is a system built around objective difficulty.
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So in 5e, your job is not to consider dramatic outcomes/momentum. Your job as GM is to consider the actual difficulty of a specific task within the gameworld
What is the basis for the conclusion made about 5e in your post above? What sections of the rules back this up?
I found some relevant rules text, on pp 3 and 58:5E is a mixture of objective and subjective; combat appears to be mostly objective difficulty, while skills are very definitely subjective. After all, nothing within the 5E wording actually says the difficulty must stay the same each time a player tries it.
Sometimes, resolving a task is easy. If an adventurer wants to walk across a room and open a door, the DM might just say that the door opens and describe what lies beyond. But the door might be locked, the floor might hide a deadly trap, or some other circumstance might make it challenging for an adventurer to complete a task. In those cases, the DM decides what happens, often relying on the roll of a die to determine the results of an action. . . .
For every ability check, the DM decides which of the six abilities is relevant to the task at hand and the difficulty of the task, represented by a Difficulty Class. The more difficult a task, the higher its DC.
[A table then lists a range of task difficulties, from "Very Easy" to "Nearly Impossible".]
For every ability check, the DM decides which of the six abilities is relevant to the task at hand and the difficulty of the task, represented by a Difficulty Class. The more difficult a task, the higher its DC.
[A table then lists a range of task difficulties, from "Very Easy" to "Nearly Impossible".]
So it seems the key question is what is meant by the phrase "difficulty of the task"? Does that mean "in game difficulty" - if so, DCs are determined "objectively" in the way that Manbearcat describes. Or does it mean "metagame difficulty" - in which case DCs are determined "subjectively", say for reasons of dramatic pacing.
The text doesn't directly answer this question, as far as I can tell. On page 59 there is a reference to "climb[ing] up a dangerous cliff", which to me tends to suggest "in game" danger rather than "metagame" danger, because the climb is certainly a part of the fiction rather than the metagame and nothing suggest that the danger is located in a different conceptual space. And there is no discussion of how to set difficulties on a metagame basis.
Also, once characters reach higher levels and have skill bonuses of (say) +10 or more, then it is no longer hard, in a metagame sense, to succeed on a check of DC 20 - yet the table still describes such a DC as "Hard".
So it seems to me, having regard to these considerations, that the more natural reading of the difficulties is as pertaining to ingame difficulties rather than metagame considerations.
This also fits with bounded accuracy as an overarching design consideration - the idea of bounded accuracy seems to be that (i) DCs are set "objectively" and (ii) the range of objective DCs, relative to character bonuses, means that DCs never completely outstrip the reach of bonuses, nor vice versa. If DCs were subjective then bounded accuracy would be less necessary, because you could always just adjust the DCs to fit the character bonuses (much as 4e does).