I think that at least Apple could put the Xcode binary files onto a CDN inside China. I'm trying to download Xcode 7.0 from the App Store today, and it's still hanging after a few hours.
And when that CDN has a hiccup dozens of iOS developers go elsewhere.
Also, this is by no means an Xcode problem only. It potentially affects every piece of software and even code rehosted from github. Does that copy of that library developed on github, mirrored on Baidu, contain a backdoor?