Quote Originally Posted by Stella View Post
I think you have this fairly wrong. The CR system is designed to determine which encounters a party of 4 consisting of a Fighter, a Cleric, a Rogue, and a Wizard of a certain level should be able to beat 3 of per day. Not which single party member should be able to beat which single encounter half of the time. If you reduce it to a single person vs. encounter fight you have broken the system beyond any recognition of the intent for its use. It isn't a perfect system by any means, but it works far better if used as intended than if used well outside of the scope of the intent.
I know how the CR system works. And actually, what the book says is that an encounter of CR = Average Party Level should be routinely defeatable with no major losses, but should consume roughly 1/4 of the parties daily resources.

A human rogue 6 is a CR 6 enemy for a party of 4 to face.
A bearded devil is a CR 5 enemy for a party of 4 to face.

Therefore, a bearded devil should be able to consume 1/4 the resources of a party of 4 5th level characters daily resources, and a single sixth level human rogue should be able to consume roughly 1/4 of a sixth level parties daily resources. It is reasonable to assume that with their various skillsets that the rogue should have a more robust set of abilities than the bearded devil, simply based on their ability to consume another entities resources.

Regardless, that is not the original point of the comment and isn't particularly relevant. The point is that the rogue and his buddies, even at level 6, are pretty hardcore dudes. Sneaking past castle guards shouldn't be a big deal for him.