My esteemed colleague, a real technical guy, has sent me some info about what you’re seeing.
This isn’t actually one of our servers, it’s something unrelated to the game. We use URLs, not hardcoded IP addresses. It looks like this is perhaps from an ad on the page, a server in Vietnam.
The headers don’t tell your browser to ignore its cache, they just tell it to validate it. If the file is unchanged the server will respond with a 304 status and 0-byte body telling your browser to use its cached file. After the first load the whole game should be cached unlessed your browser overrides the headers.