I definitely have to agree with this. It has lead to "it works in my sandbox" but breaks in our staging enviromemnt issues at work since everything in staging goes through a proxy.
Well, I don't agree. It is certainly a nice addition to make the web more secure. I hope my bank (and every other significant website) won't toss my auth tokens to different domains. And about reverse proxies: it's a browser feature, so how can reverse proxies be a problem? The browser doesn't care what's happening behind a reverse proxy.
Instead, let's solve zero day advertising payloads.
Let's fund a cure for email spam and phishing.
Let's find a cure for site spoofing.
Let's find a cure for "this dialog means I have to click OK to get on with things."
Regarding "domains are controlled," that doesn't matter. If I want to serve pages from www.mydomain and static/CDN content from static.mydomain and services from api.mydomain, those are different domains.
The main solution for a big site is to build all the credential and security logic into the load balancer/HTTPS terminator, which is an almost-guarantee to get version skew and security holes.
All this "secure web" intention only works for small monolithic sites, and don't even solve the real security problems on the web.
I thought that an attacker's JS code can't read the response from a GET request in a CSRF attack. Or are you saying it's possible for the attacker to read the HTTP status code of the response?