To be perfectly honest, why are you worried if you end up mis-connecting? Certainly Qantas will put you on the next flight, provide hotels and meals, and provide up to 600 Euros in compensation should you arrive at your final destination of Perth more than 3 hours later than scheduled. These are all required under EU261 which applies to all trips originating from Europe irrespective of who is operating those flights, and irrespective of where the disruption occurs along the way. Just remember, the airline which causes your disruption will be the one you'll need to go after for collecting that 600 Euro EU261 entitlement. For instance, flying Frankfurt to Sydney last year (via Helsinki and Singapore), the last leg in my trip SIN > SYD operated by Qantas was delayed by 14 hours. I filed a claim with them for EU261 compensation and sure enough the next day they agree to fork out the 600 Euros plus reimburse me for the hotel and ground transfer I had to pay for in Singapore.
-RooFLyer88