About passive perception, I have a player with a level 7 Cleric that is sitting at a 19 in Wis and is likely to take the Observant feat at level 8. His passive perception will be 23 which is crazy high. This seems oddly powerful to me. He is going to notice everything all the time. Am I over-reacting to this a little? Also, if he actually makes a perception check and it comes up lower than 23, can he just use the 23 pp instead? How do you even RP a perception check of say 10(if he rolled a 2) if his pp is 23?
A couple things to note here as you attempt to DM this stuff...
First for a bit of math clarification... shouldn't his Passive Perception only be a 22? +4 for Wisdom, +3 for Proficiency bonus, +5 for the Observant feat? Or is there another modifier in there I am missing?
Second, don't forget that if anything that is hidden or to be noticed is in a
Lightly Obscured area (which includes
Dim Light), finding it is at Disadvantage for the seeker. Which means for Passive Perception it gives a -5 penalty to the passive number (effectively cancelling the +5 bonus to the passive number the PC got for having the
Observant feat). Which means their Passive Perception for anything in Dim Light is only 17. Still high, but at least a bit more manageable. Yeah, if the Cleric becomes the de facto trapfinder of the group and walks around with a
Light spell on his weapon (for example) so that anything he searches for is up close is within Bright Light (thus moving his PP back to 22) and it'll be harder to catch him with some traps... but at least monsters that are hiding out in the dimly lit area will have a better shot at remaining hidden until they attack.
Thirdly... how you run the Passive number versus when you call for an Active check (and the number ends up less than the Passive one) is up to each DM. Speaking personally... I treat Passive Perception as the baseline "always checking" number, which find anything and everything automatically that is less than that, no rolling required. So if a goblin is in the shadows and their Dexterity (Stealth) check came up as an 8... every person with a PP higher than 8 notices the goblin, no rolling required. However... if something is hidden out there whose Stealth check or DC to find is higher than the PPs of various characters, I will allow them to roll an active Wisdom (Perception) check, in the hopes that they roll over a 10 (and thus increase whatever their check number is over their passive one.) If they roll less than 10 on the die (and thus their check is less then their passive number) then they did not learn anything they didn't already know from their passive perception. But those who rolled higher than 10 on their die roll increased their total Perception over and above their passive (and thus possibly can find the hidden creatures or features that were hidden.)
Others rule their use of Passive and Active Perception (and Investigation) differently... so it really comes down to personal DM preference. I myself have a PC in my group with Observant, and more often that not... rather than just make it a number bonus to his rolls, I come at it from a story perspective and oftentimes just grant him noticing things automatically because he's just really, really observant. So for instance... if there are sounds coming from down a dungeon corridor and he's moved out ahead of the party on point... if my instinct is to request a Perception check I oftentimes will not even bother having him roll and just tell him straight away "Due to your keep observation skills, you notice blah blah blah..." This way he knows that his spending of one of his precious feats slots on being a hyper-observant individual is actually getting some use in the story, and he feels really good about it.
