There is a lot of information out there on varroa and treatment vs. Treatment-free. Tom Seeley is one of the most respected bee researcher in the world. This video is well worth the time it takes to watch.
Notes
Wild bees colonies have a 100% survival rate
Many of the large producers of bees fail from Varroa
Wild colonies and VSH queens have very high survivability
Spacing hives by 20 m or more greatly reduces "mite bombs"