The unavoidable triggers and RNG "stealth checks" are ridiculous. I would consider it fine if they were rare, but they really aren't, and stealthing rooms feels too out of the player's control too often. If you want a perk to improve stealth, it should only be to reduce the distance the sounds you make travel and reduce vision of enemies. Not give you better odds rolling dice when you walk over invisible thresholds.
Hmm...you may misinterpret how the system works. There are no RNG stealth checks. Whether you are detected and/or targeted is strictly based on:
1) how illuminated you are
2) how much noise you are making
3) the zombies' detection ability (differs per zombie, so I guess there is a little RNG here: Arlene #1 might hear slightly better than Arlene #2)
If you cross a sleeper threshold, #1 is compared to all zombies' vision in the sleeper volume. Line-of-sight is ignored and that is arguably a Bad Thing, for sure! IIRC faatal said [or maybe it was a comment in the code] that this mechanic is a temporary stop-gap to get the system mostly working). But in any case there is no RNG component to "do I wake up the sleepers". There are
some volumes (though I think it is more rare than players believe) which will always wake up when the player enters. "Scripted fights" if you want.
Edit to add: okay not really. Reviewing our investigation in the older thread, the "worst" type of volume is an Attack volume, which gives the sleepers that ignore-LOS check to "see" you. In some cases, the volume might be designed - i.e. with zombies in the ceiling right over your head - so that that check nearly always succeeds and the zombies target you. But the volume is following the same rules as any other Attack volume, say one where the zombies are more spread out and don't have such an easy chance "seeing" you.
In my testing in the older thread, though, I was able to safely traverse a few volumes which players thought were "auto-attack" volumes. I needed several levels in the stealth skills though, and shooting out lights definitely helped! (Why don't the shots wake up the zombies?!? Gooood question...it definitely ain't perfect.)
If there are awake zombies around you, then they can detect sounds which, again, have no RNG component at the moment the noise is made. (As mentioned there is an RNG component giving small boosts/nerfs to individual zombies' hearing, but this is done at spawn time, not for each noise.) If the noise a) reaches the zombie and b) is above the hearing threshold of the zombie, it will go investigate the noise (but not necessarily target you!). Your stealth skills and equipment can muffle noises.
If a zombie is facing you, then we're back to player visibility vs. zombie visual acuity, but with line-of-sight considered of course. No RNG component. Your stealth skills and equipment can make you less visible.