How useful is studying MSc Computer Science in Switzerland?
EPFL is one of the better technical universities. This has two consequences: 1) it will be hard (as @xLeitix notes, if your current school doesn't even teach complexity, you will be in for a challenging time at EPFL), and 2) you won't have a problem to get a job afterwards.

Note that differences between schools are not as pronounced in Europe as elsewhere. For instance, I am pretty sure that you will not be able to attend a German or Swiss university without exposure to algorithm complexity. Consequently, employers (both academic and industry) in Europe don't really care all that much about school quality. Grades, internships and the impression you leave at the interview are much more important.

Beware of costs of living in Zurich. Zurich compares with New York City. It's horrendous. (I used to live there.) Lausanne should be somewhat better, but Switzerland is generally an expensive place. If you seriously plan on going there, check local rents and/or supermarkets (coop.ch or migros.ch - you should be able to find this week's offers even without speaking German) and convert them from CHF to AUD to get an impression.

Note the language: Zurich is German-speaking, but Swiss German is very hard for a non-native speaker, even if you did take German classes. Lausanne is French-speaking, and the Swiss French is closer to "standard" French than Swiss German is to German. Francophones dislike speaking English, so you will get by more easily in Zurich than in Lausanne in English.

Switzerland is not in the EU (although it of course cooperates), so your EU membership is not all that important. With an ETH/EPFL diploma, you should have no problem getting a job anywhere in Switzerland or the EU.