To add or not to add mechanics news

Yesterday we kind of hit a wall while designing a section of catacombs that the player has to get through. I got frustrated because it felt, in my mind, boring and empty of things for the player to do or interact with.
When we get into discussions about things like this Amnesia: The Dark Decent always turns up as example. In Amnesia the physical monsters do not show their ugly faces until about 40-60 minutes into the game. We all agree that this is a great design choice: it makes that monster a lot more frightening because you have been waiting for it, expecting it at every turn.
Implementing that lesson is not as easy though, it goes against almost everything else you are though as a designer: walking is not a mechanic, players want to interact with the game as much as possible, give the player tools and let them use them in diverse ways etc.
As we move forward testing will of course serve as a measurement tool for situations like this: The players will likely tell us a lot more about how much interaction is enough than in-team discussions ever could. As soon as I left "the office" (we work at the university, so it's not really our office) new ideas sprung forth and today we made a few subtle changes to the area. Instead of adding a combat element we decided to focus on exploration and forcing the player to really study their environment in order to progress.
It's not a huge overhaul, but it might make all the difference. In the end I believe that it is the small things: the sounds, the shadows and the whispers from the corners that enables the player to create their own horror, and seeing monsters even when there are none.