Yeah, I mean part of it is balancing the attributes and exp gain in general. There are a lot of ways to do it.
I am not sure where I would put it in other attributes... Strength and Intelligence do not really need it lol.
I think In the shadows would be pretty safe though, because the power gaming it would encourage is really exactly what you should be doing as a sneaking agility build.
You would be trying to sneak around and get every kill you could with a sneak attack, and you might want to run around at night sneaking to get kills, with the risk vs reward of what might spawn, heh.
Plus, then people would get it early and probably sneak attack damage and realize how fun some POIs are and see that a lot of the jump scares will not trigger while you are sneaking.