Ok, here's my experience w/ DWV.
I've been practicing the (MDA splitters) brood break therory, for mite control, and I have found when the mite population climbs, so does DWV, while I do believe DWV is there and real, how many bees are observed with deformities from the mites feeding and mistaken for DMV?
There are camps that believe that you can't even do a hive inspection while the queen larvae are forming to prevent deformity. The mites ain't exactly playing patty cakes while they're in the cell with the larve.
Can't answer your question on the vaporizer, but with your being down south, you've already got brood right? Doesn't that mean you have to do multiple treatments to be effective?