I have followed Australian cricket since last 30 years and believe me defensiveness, negativity, selfishness was never a part of their culture. They are mentally very strong, always play with positive attitude and aggression. Forget about T20s, you need to see Ricky Ponting's inning in 2003 WC final or Gilchrist's inning in 2007 WC final, in such a big match they came with a plan with particular target in mind rather than leaving it on their middle order or tail. In 2015 WC QF against Pakistan, they were 3-59 in a chase of 214 and still they had finished the game in 34th over. The best thing about Aus is their batsmen rotate the strike very well in every format and they look for at least 1 boundary in every over, that's why they score at minimum 5-6 RPO in ODIs.
Pakistan team management must kill this culture of defensiveness, negativity, selfishness in every format not only in T20s