I'm going to use the definition of resistance as bees that actively kill varroa and/or prevent varroa from reproducing. I will use tolerance to refer to bees that tolerate the effects of a large mite load. By this definition, VSH bees exhibit a resistance trait and Ron Hoskins bees with DWV type B exhibit a tolerance trait. There is nothing to prevent bees from exhibiting either, none, or both mechanisms.
Bees that express too much VSH remove too much brood. I had that with some of the Purvis queens. That is why I selected away from his line in 2005 and 2006. VSH has to be in the mix for bees to have a high level of resistance to varroa. My bees exhibit good to very good levels of grooming and mite mauling. Between grooming traits and VSH traits, it is possible for bees to maintain a productive colony while keeping varroa to levels that are nearly undetectable.
So to answer how "high", if I see any detectable varroa mites in a colony of my bees, I requeen that colony. This level of varroa resistance came at a price. My bees swarm more than I like. They shut down brood rearing at the least hint of pollen being unavailable. I purchased the Buckfast so I can cross them to my line and bring some of the production traits back into the mix. This means having to compromise over the next few years because Buckfast have low resistance to mites. I will probably have to treat any pure Buckfast colonies next year and may have to treat them this fall.
Noting in passing that JBM and Hoppy are happily engrossed in passive aggressive behavior. Maybe Hoppy can get a job in environmental management at Trump's golf course in Scotland and get them to hire JBM for border security. I'm sure Trump will see the wisdom of having two professionals on his team!