Well .. not much there that I would agree with Afermo !!
1. Swarms are not often disease ridden mite infected colonies ... the ones I've seen and collected have been really nice LOCAL bees that have formed strong colonies very quickly that have gone on to be good bees. The post swarm comb building is something of a miracle to watch and even the bigger swarms seem to be reasonably easy to handle for a beginner, as they always seem to be intent on getting on with building their colony. Swarms can be free or at least of little cost compared to the cost of a nuc it's a no brainer. Even if they turn out to be a duffer you can still buy in a good queen for £30 or so and you then have better bees for a fraction of the cost of a nuc.
To this date, i have never caught a diseased swarm, or one that has developed a brood disease a few weeks later. (Chalk brood not included, that is sometimes there, but thats "sortoutable")
I argue that if a colony has made it to swarming stage, and its of reasonable size, its pretty healthy, period!
However that dosent mean i dont check and also put the swarm in a furthest away apiary, just in case but saying that, I've caught feral or wild swarms in all of my apiaries, so sometimes i wonder if its worth the late night moving!
I know bees are known to migrate due to adverse conditions in their current location, but swarms in May and June and some of July are more than likely to be healthy.
Their queen may well be old, but thats another thing to deal with.
Often a smallish swarm builds comb and the queen then lays a couple of frames and dies. This dosent mean it was diseased, its just a queen that wasn't that strong, or is swarming for perhaps her second or third time!
i cover my options and remain open minded. Theres Lots of "guff" talked about it most of the time!!
For me its something i am interested in. If we are ever to hopefully search for bees that have traits like groom mites (ankle biters) and bees that have a tendency to yank out diseased larvae from under sealed brood, and similar for mites, and others we are yet to discover, we should never dismiss this opportunity to try this survivor stock.
Everybody has their own ideas, but bees will evolve. How on earth wild or feral AMM have coped with Varroa so far is the big question.