I've read (and experienced with my Carnolians) that oxalic acid treatments can sometimes take more toll than the mites themselves. Any thoughts about this? Have you had any causalities with its use?
As far as pesticides, I am sure they harm bees, but CCD has pretty much gone since the aggressive treatment of varroa started. Russian bees are thought to have brought varroa with them. Before that there were pesticides and most were much more toxic including DDT but the bees were just fine.