Virgin Atlantic pulled out of Sydney - Hong Kong because they aren't a hub airline like Cathay and the Gulf Airlines. They have the same problem as Qantas. Cathay can fly you all over their network from Sydney via a stop in Hong Kong where as Virgin Atlantic could only offer London.
Europe - Australia is high cost, low yield, the airlines based at either end can't compete with the enroute hubs offering one stop multiple destination options. Middle Eastern and Asian Airlines enjoy significant cost advantages with aviation friendly governments and employer favorable employment laws.
A business class return ticket London - New York is the same price as London -Sydney but is one third of the distance with no enroute stop.
Aviation is seeing a transformation in the way people fly long haul, only a few routes such as Sydney - Los Angeles and Europe - US East coast are safe from enroute hub operators for the moment. EK and SQ would love to get SYD - LAX and it could happen if the government decided more competition was needed.