I keep my pup in the basement as well, but we all live down there right now because we're doing renos. We're "Cellar Dwellers"!
It may just be the fact that the area is much closer and damper quarters with lower ceilings than the rest of the house, so the smell is much more concentrated. I know I've walked into the room and been wafted with a good hit of "eau d' chien", but there is no other option at this point. In the OP's defense, I can say that basement does not equal isolation, it's just a different level of the house.
I have yet to meet a dog with "zero smell". I think as owners, we get used to the smell of our pets and notice the smell less and less.
It sounds like you're being crazy meticulous with the bleach cleaning and air fresheners. A rottie will never smell like a rose.
I would be tempted to take a closer look at your pups diet. I'm by no means and expert on raw but I though that variety was of some importance. Different cuts and varieties of meat, bones etc. veggies or supplements?
I'll be curious to see the outcome of this thread.