Post WC 2015 Australia defense(bowling) has weakened. They have lost their strike bowlers to retirement & injuries.
And the current lot of bowlers not only lack in penetration but also cannot defend a sizable target(excess of 275 score)..this despite the introduction of new ODI law of having 5 fielders outside the 30-yard circle!.
Below table is snap shot of Australia bowling performance series-wise.
A comparison of first table of WC2015 v/s post World Cup