I agree with you that QT is probably the biggest killer of fish (once leaving the LFS). I agree about the stressful conditions in a qt and medications that curb appetite causing strife.
I am all for NSW and feeding the highest quality, natural foods, live foods.
If it was just ich, I would have invested in a bigger uv and stuck it out...that's why I got the uv in the first place and it kept ich nil on my 150 for many years.
But this time was different, it really looked like velvet and was spreading to my other fish. In fear of losing everyone, decided to try Copper Power at 2.25 for 2 weeks...I know folks will say 2.5, but I have time to observe.
So far, everyone is eating. I have done my best to provide the least stress possible qt tank...sand, plastic plants, plenty of pvc, natural light source and no reflections of a glass qt in a black Rubbermaid. Minus the jawfish in the net boxes (each with sand bowl, pvc and shells) and clowns in the colander, the rest of the gang are acting normally in the Brute (tangs being tangs, wrasses investigating the sand, hawkfish perching about, angelfish keeping track of everything...).
You have some beautiful fish. Are they all from sources that quarantine them? Do you do observational qt or just put them into the dt? I am assuming you've had ich and manage it with the uv, but have you had velvet?