While I agree that rotating might be a net negative, that particular issue could be worked around: hash the FQDN and use the hash to determine which provider yo

While I agree that rotating might be a net negative, that particular issue could be worked around: hash the FQDN and use the hash to determine which provider you use, so that a given user always resolves a given FQDN with the same provider. (Salt the hash, so that different users use different providers for that FQDN.) It's still not clear if it's a win to rotate, but if you were going to rotate, that would help.