It's a pretty sophisticated arms race that's lead to some cool stuff, notably pluggable transports (like the obfsproxy you mentioned): https://www.torproject.org/docs/pluggable-transports.html.en

Unfortunately the companies that enable this deep packet inspection are often American companies working overseas. My friend who used to work at Cisco said they had internal slide decks about the improvements they could make to the Chinese firewall. Then there's Bluecoat in Sunnyvale (https://www.bluecoat.com/) building the censorship systems for the middle east.

Why do American companies sell this kind of stuff to China and non-democracies in the middle east? They must rationalize it in someway, but I think it's wrong.