I am fine with NATs! I think is a good compromise between security and connectivity. If two users want to connect they have to explicitly do NAT traversal.
Wasn't mDNS designed for small networks like intranets, not the whole internet?
I'm reading a discussion on Google where in the comments it is mentioned that you can still obtain IP addresses even with mDNS enabled if you're allowing video and audio with a specific flag set (again with the configuration implementation.)
'IP Leaking' was fixed with mDNS candidates [0]
[0] https://tools.ietf.org/html/draft-ietf-rtcweb-mdns-ice-candi...