I'm the dev/designer at Firebase who made Vulcan during one of our experiment weeks. I've been using it for pretty much all my Firebase development since. Let me know if you have feedback!
>Fast forward to 2014 and Chrome’s DevTools now leads the way in helping developers debug JavaScript<p>I wouldn't say Chrome's DevTools are significantly better than Firefox's native JavaScript debugger. Both are pretty identical in terms of features when you look at the latest versions.