But, if you also introduced a life threatening parasite to that population that had no natural defences to that particular parasite then there would be another level of nature's interference to the common good to contend with. Perhaps one in a thousand may be able to survive alongside that parasite and find a way to manage their existence.
Well, we can both pluck numbers out of the air. What is the average (unassisted) survival rate of:
a) bees entirely deviod of defences against varroa?
b) bees with fully developed resistance?
c) bees at any point in the spectrum between those two?
So - Sadly, your analogy does not totally hold water.
Your conclusion doesn't stand up, You need real figures for every point on the spectrum in order to make your case, and you need to specify which point you are on in every statement. One-size-fits-all thinking doesn't cut it. It just creates muddled thinking.
I think evolution in insects is much faster than those creatures who have long life cycles and I also believe that both some honeybees and varroa mites are evolving to accommodate symbiotic living ... But - we are not at that stage yet where it is genera within our kept bees or even where these traits are commonplace. In order to prevent the potential for massive colony deaths I think there are going to be colonies that require treatment fpr the forseeable future.
For the first part you are right - evolution is faster in rapidly reproducing species.
For your next you are assuming worst-case in all cases. That fact is: some are already deeply adapted, while some are entirely unadapted. (No prizes for guessing where you find each category.)
So your concludion holds most for the least adapted end of the spectrum, and least at the opposite end.
But not universally. Not all bees are equal in terms of adaptation to varroa at this point. Not by a long chalk.
The key to successfully managing varroa is to test for the infestation levels regularly and monitor those colonies which appear to be more susceptible to the mite and treat those and the ones that have low levels of mite allow them to continue without treatment - and monitor.
In breeders terms that is not a long way short of the worst possible way to go about things (that would be to make increase _only_ from the ones that need treating. I'm sure you can understand why that would not be a good plan...).
An infinitely better route available to you is to re-queen from those that don't need treating - or need least treatment.
Always bear in mind that there are many factors that affect varroa ... and my belief is that allowing natural levels of drones to be produced and insulating hives to allow high levels of humidity and colony temperatures are key factors. I think, also, that stressed bees are more susceptible to varroa so low levels of interference in the colonies is another important factor. Not let alone beekeeping - just keeping inspections light and quick.
Well, the art and science of locating and breeding in resistance is available for anyone who wants to try it. For those with just a few hives, local breeding groups are the way to go - unless you are fortunate enough to live where wild bees have done the work, and support you. In which case try to avoid undermining them by sending unadapted genes into their ranks.
As to pet theories - there are lots, and you can take your pick.. I still stick with starter strips in the brood nest, in case cell size is a factor.