I would like to offer my perspective on why this is an issue for many of us, myself included. I created my account just to reply to this thread. So, hello all!
It has been stated that TFP want moments of direct confrontation in POIs. An understandable design decision. But the current handling of auto-aggro volumes in POIs is bad design. And I will explain why I say this.
I currently have over 2000 hrs played, I mod my game to have to have 4x zombies with respawn rate of 4 times a day, and my wandering hordes are 20-30 in size. So I get plenty of direct confrontation in the game. And I have played practically all weapon builds. With that said, when a game, any game, offers stealth options as part of game play, I tend to gravitate toward the stealth/sniper style of play. I just find it very enjoyable.
Now, I think we can all agree that games cheat. They know things the player does not, and they make decisions for reasons of game play, optimization, or whatever. When I stealth through a POI, the game knows I am there. But for immersion it pretends to not know I am there. It needs to do this in a way that makes me, the player, believe it is my skill and my character choices that are being rewarded.
In the current form of auto-aggro volumes, no matter my level of skill or perks, even if my stealth meter is on 3. The moment I set foot in the volume, the Z's aggro. It does not matter what I do. Venturing through the same POI layout, the first time - "Oh, crap!". The second time - "Really?". The third time - "This is bull, the game is cheating." And I have played enough that I know where pretty much every single auto-aggro is. It is no longer "Oh, crap!", it's just "oh, this one again. No stealth here."
A simple change of making auto-aggro volumes not 100% activation can fix this. If they had some percentage chance to trigger, regardless the player's stealth, that adds your direct confrontation moments. But when done well the player does not get the impression the game is cheating. If we didn't know auto-aggro volumes existed, over time, a very astute player may figure out that certain areas of POI's are tricky and dangerous to traverse, but many would just assume bad luck. And there would be a lot more of the "Oh, crap!" moments.
edit - also add a delay, entry of the volume can trigger the event (percent chance), but the aggro action does not occur until after some random time has passed. This would make it harder for the player to determine a pattern, which is obvious as it is now, with immediate aggro.