I agree that QoS is a decent solution for the SNO side if the connection is a bottleneck. Though not all routers have it. A friend of mine had to stop their node because the router had no QoS and the internet was no longer working. Admittedly they had a connection well below the recommended spec.
If the HDD is the bottleneck, a possible solution could also be to spin up a second node, which will spread the load over 2 HDDs. There are several options SNOs could consider.
But I’m afraid as long as the max-concurrent-requests setting is there people will use it.
As for success rates, that was not my primary concern when posting this. I don’t doubt your results, but I’ve also seen SNOs that had rates below 10% and were able to significantly increase them by rejecting about half of the traffic. It could go either way. Though I’ve stopped suggesting it to people due to the issues it could cause for customers.
Even if people don’t use that setting though, selecting nodes that aren’t already slow could also increase performance for the customer. I see many SNOs touting gbit connections with plenty of room to spare. They can probably handle a little more load while the slower ones are struggling.