Question: What i'm wondering is, what kind of behaviour does google analytics show when a ddos attack occurs? Any theories?

Answer: 
It will show up 100% some significant peaks in google analytics , simply because there are huge number of requests from multiple sources having huge bounce rate !
When a HTTP DDoS attack occurs the attacker is either using several (thousands) of computers to do so. Sometimes, it's also done with servers. When they make the request, they don't render the javascript or anything - they simply in most cases just make a GET request to the webpage.

So no, it shouldn't *really* have an impact on GoogleAnalytics