Here's my video guide utilizing Hermes Proxy to allow the 1.14.x and 2.5.x Classic clients to connect to a Vanilla 1.12 or TBC 2.4.3 server. I also show how to disable Warden and Strict Version Checking on a VMaNGOS or CMaNGOS server to get it all to play nice.
https://youtu.be/qsJSL7I0nak