Where are you getting reliable mDNS? I love the protocol on my own devices but good lord the Google Home ecosystem is terrible. Playing audio through multiple speakers at all, forget getting them in sync, is an exercise in frustration. And when I check by scanning mDNS it's always hung getting no responses from devices I know are there.
The literal Chromecast itself seems to be exceptional device that just works.
Been using mDNS for years in the Apple ecosystem. Never had issues, except maybe 5-6 years ago with AirDrop but been rock stable since. Using airdropping, sharing screens, printing, audio, all kinds.
The literal Chromecast itself seems to be exceptional device that just works.