#1. Proper Defensive Cover:
Ideally, there should be at least one or two players behind the main line when a team is building an attack so that, a) when a player is passing the ball, there is always a defensive cover for him if he plays a wrong pass or his pass is intercepted and b) the scrum half has the option of playing a 10-15 meter backward pass instead of always passing it sideways.
Passing the ball back backwards to the full back means that he can then kick it to the touchline or opposition territory. This offers the team a chance of gaining territory and also ensures that they do not lose possession inside their own half. I did not see the Australians doing that and instead, they went gung-ho and attacked without any defensive cover. As a result, when a Wallaby pass was intercepted by an opposition player, he ran unchallenged to score a try.
In the Autumn tests against the visiting Australians in November last year, England and Scotland scored 2 tries apiece after intercepting an Aussie pass. This scenario needs to be avoided altogether. Australia have some very good defensive players like Kurtley Beale and Reece Hodge and those players should stay behind the main line to ensure proper defensive cover.