[5e] The Disadvantage of Disadvantage

Post date: Jan 30, 2015 6:51:56 PM

You’re really screwed if you’ve got disadvantage in most cases. The

only time you don’t is if you were almost guaranteed to succeed before

you got it. If you need a 11 to do something, you've reduced your chance

from 50% to 25%, that’s the equivalent of a -5, and that’s on an

average needed roll, which is where most things should be in the bounded

accuracy of D&D. This means you might as well do something else than try

to do something with disadvantage. In combat you’re effectively

wasting half your rounds if you normally hit about half the time. If you

need a 15 you’ve gone from 30% chance to 9% chance, about equal to a

-4, but also means you’re wasting 2/3rds of your rounds. Say needed to

roll a 20 though, you've now gone from 5% to 0.25% chance, 1 in 20 to 1

in 400.

Let’s illustrate this. You’re an archer trying to hit a far away

target in the bullseye - you normally don’t have much chance, about 1

in 20 of your arrows hit it. Now we cover half that with a board.

You’d think it should go to 1 in 40, but by 5e D&D it’s given you

disadvantage, so you now have a 1 in 400 chance of hitting it. It’s

almost as bad to me that disadvantage is nearly meaningless to those

good at something. If you hit on anything but a 1, disadvantage would

make that from 95% to 90%, the equivalent of a -1. Taking that same

archer scenario, say it’s 10 feet away and the archer gets 19 of 20

shots in the bulls-eye, we now cover half of it with a board, and

that’s 18 of 20 shots.

Typically in 5e with bounded accuracy you should be around the succeed

on a 10 range, which means disadvantage is typically equivalent to a -5.

- Justisaur