Yep, I've been tempted to pregenerate a list of rolls and just use them straight down the list. I think if the players never seen me roll though they would dislike that. However, maybe a mix of rolling for certain things but using the list when I want a check for something I don't want them to know I'm rolling.
I don't see anything wrong with comparing two passive scores to arrive at a result when the associated tasks have uncertain outcomes.
For me it's because you have eliminated all chance in respect to the outcome without having roleplaying back up the chanceless outcome.
In general, I don't see chance as desirable. A d20 is nobody's friend.
As far as the roleplaying, the player made the decision as to what ongoing activity or task the character was undertaking (keeping watch for dangers, for example). Unless you mean something else by "roleplaying."
Your general principle of play smart and avoid chance rolls is admirable, and you are a strong advocate of it. However, changing what should be a random roll with a method that produces no randomness is the problem I have, and that problem has nothing to do with avoiding random rolls by playing smart.
So saying a d20 is nobodys friend is true only in the context that if you can play (aka roleplay) your character so he auto succeeds then it's better than rolling. But don't confuse concepts. When it comes to even considering ability checks we are only looking at times where the DM has determined that there is uncertainty involved in what you are doing. What I'm confused with is how someone with your stances can advocate an "uncertainty resolution system" that involves no chance in resolving uncertain situations?
Uncertainty is resolved with an ability check. A passive check is an ability check.
That leaves nothing to chance, though. It's auto success or auto failure. No uncertainty is present.
"Uncertainty" refers to the DM's assessment of the outcome of the task being performed, not to whether dice are involved.
You weren't uncertain, though. You were just certain via a different method than deciding straight out.An ability check or a passive check resolves the uncertainty in the fiction and gets the DM to an outcome. Whether it's an ability check or a passive check depends on the stated goal and approach.
That doesn't change anything, though. If PC A has a passive perception of 14 and you have a DC of 15, there is no uncertainty on your part, either. Same if the DC is 13. When you have two set numbers to determine an outcome, nothing is uncertain. Uncertainly only comes from not knowing whether success or failure will happen. You need random rolls(or some other type of random determination) for that to happen. Otherwise, the outcome is certain.
You weren't uncertain, though. You were just certain via a different method than deciding straight out.
Here's an example.
Player A wants to climb the mountain. As DM I can decide outright that he succeeds or fails. That is a method of resolving the issue with certainty.
Alternatively, I can involve an extra step of setting the DC higher or lower than the PCs passive climb score. That's a different method of resolving the issue with certainty.
Lastly, I can call for a roll if I don't know for certain whether the PC will succeed or fail.