Quote Originally Posted by Skrum View Post
On this subject, I'm in the process of writing a skill guide for DMs. It's mostly about how to set DCs - and my main position is most DCs should be pretty low. Like under 10. A +7 on a skill is extremely high relatively to the average person (for context, the PHB defines the average person to have 10 in each stat and no skill proficiencies). Is the average person pretty unlikely to climb a tree? That doesn't add up to me.

DC 8 or 9 seems much more appropriate, if the tree was not a good climbing tree. The average person might be able to climb it. Someone with +7 athletics? I should be damn near automatic.
I totally agree and the DMG kind of backs you up here. There's really only a handful of DC's given in the book, but barring Purple Worm Poison's Save DC of 19, few (if any) DC's given for traps etc. go above 15. I think it might be a holdover from 3e that has people setting DC's of 15+ as a matter of course, but 5e really doesn't support that magnitude. DC:15 is a Medium difficulty for a task that's already been determined is a challenge. That's the baseline. Even an Easy DC of 10 or Very Easy DC of 5 comes with the assumption that there is a possibility of actually failing. If there's no risk involved, you simply don't roll dice at all.

It's also worth noting that there's no automatic fail state for ability checks; a 1 is just a low number. As your modifier to the check increases, so does the kind of challenges that you automatically pass and that's also part of the heroic nature of Player Characters and their adversaries; that they can routinely pull off tasks, often without fail, that other, untrained regular folk find challenging or even impossible.