We've had
hyperlegislation against the terrorist threat here in Australia, and aside from the financial regulations, virtually to no effect except the loss of civil liberties.
The laws covering financial transactions have been effective in combating both terrorism and organised crime, making them one of the few worthwhile changes.
The most noteworthy/publicised Australian terrorists have been converts from non-muslim backgrounds, so it's unlikely that screening will be particularly effective.
As a percentage of our immigration refugees are a tiny minority, we do screen all refugees for their history and extreme views though.
I think the Australian government should take more of an interest in Muslim clerical leadership in the country.
We don't want Salafist Imams from Saudi Arabia or their money. Given the region and it's history of Islam, a regional Muslim clergy with a relationship with the Government could avoid a lot of issues and provide a line of communication to otherwise cloistered communities.
Boot out any radical Imams where possible. Don't take more refugees than we can successfully integrate (don't create isolated communities of ethnic underclasses).
I think scaling back the idea of a "Big Australia" will prevent more social problems than giving police powers of mandatory detention and unlimited surveillance.