TURN/ICE is supposed to work just fine on symmetric NATs. Chrome even supports single-socket TCP relays, which can't be broken easily by any sane firewall. I personally have a few boxes testing it with only TCP 80 port allowed and it still finds a way to connect. A few tricks on the TURN side have to be employed but it's pretty robust. Whatever issue the OP has to be a bug or configuration issue. There are known problems and I still see a lot of freezes, protocol or hardware compatibility issues, CPU overload and so on, but straight Chrome to Chrome connections seem robust.

I'm not convinced.

WebRTC is supported by huge corporations with massive resources. If they had decided to use IPv6 instead of SDP for addressing, I can't imagine there would be any difficulty in user adoption, and they could only improve service adoption.