No, WebRTC is not extremely buggy, nor is our signalling server unreliable. multiplayer.scirra.com runs on a dedicated server with a 1 gigabit direct connection to the Internet (there is no NAT).
The problem is the Internet itself is sometimes unreliable. The quality of a connection between two random devices on the Internet is highly variable. If you cannot get a reliable connection to the US-based signalling server, running your own server closer to you is one possible solution, but that's not because WebRTC or our server sucks, it's because sending data over thousands and thousands of miles across the planet's surface is not a perfectly reliable process.