Is that enough though? You may have wildcards on domains that are not even on a public DNS and you may forget to replace it "somewhere". For that reason it is better to either dump list of domains from your local DNS or have e.g. zabbix or another agent on every host machine checking that file for you.

That's exactly my point. Is that while this service sounds quite useful for many common cases, it's going to fail in cases where there's not a 1-to-1 certificate-to-server mapping. Even outside of wildcards, you have to account for cases where the cert might be installed on N number of load balancers.