Not sure what you mean by sneaking isn't viable. My primary mode of attack for POIs is sneaking. With the sneaking perks, sneak attack perks, books, and armor mods. You can easily clear factories or 6flr Apartments without waking up anything. Trouble is the irradiateds that can tank a x4 sneak hit from my t6 bow and steel arrows. Even when they do wake up, so long as you stop moving and let your meter drop, you can lose a zombie that is standing right in front of you.
The sneaking perk also muffles your actions by a pretty decent amount.
I could see bonus xp for sneak kills, but if you pla