Deputy Queensland coroner John Lock recommended the Australian Defence Force review its communications processes after he found an order from headquarters to increase security at patrol bases never reached troops on the ground.

Mr Lock's findings on Tuesday followed an inquest into the deaths of Corporal Stjepan Milosevic, 40, Sapper James Martin, 21, and Private Robert Poate, 23, in the "green on blue" attack in Oruzgan province on August 29, 2012.

Private Poate's father, Hugh Poate, said the coroner's findings had brought the facts out into the open and vindicated the push by the families of the three soldiers for an inquest, after an internal Defence investigation released in September 2013 made criticism of low-level officers.

"It was very badly led by the chain of command," he said.

"We knew this case was not going to bring our boys back, but we also knew the findings of the internal investigation report were superficial, and were not complete ... the only way we knew a lot more was because of soldiers in that taskforce."

Mr Lock said a major spike in insider attacks in Afghanistan in 2012 had led to an order from the NATO-led International Security Assistance Force, released on August 13, that emphasised security, including separation of Afghan soldiers from mentoring troops and the employment of armoured guards.

Afghans had been allowed to continue to mingle with the Australians, there was just one Australian guard on duty and the Australian platoon was dressed in gym gear rather than uniforms and body armour when Afghan National Army Sergeant Hekmatullah gunned the three men down less than three weeks later.

Mr Lock said no one could know whether the precautions ordered, if put in place, would have stopped the killer.

"What we do know is he would have seen a quite different defensive setup and posture compared to the relaxed state of affairs he had seen during the afternoon and early evening," he said.

"That may very well have deterred him from attacking then, or if it did not, the greater readiness of the platoon could have provided more opportunity to take more immediate defensive action, which could have prevented at least some of the deaths."

The coroner recommended the Australian Defence Force review its communication and intelligence processes, and the training given to mentoring troops. He said there appeared to be some resistance to changing the mentoring strategy "whereby rapport and development of interpersonal relationships took some priority over force separation".

He slammed the top brass's planning for insider attacks as "uncoordinated" and as apparently "a tick and flick process" that wasn't taken seriously by some.

Mr Lock said there were "personal errors of judgment" in relation to force security by two officers at the base, but the situation indicated a failure at a number of levels in the chain of command.

A Defence statement said the organisation took action to address any issues of safety or security found by a review or inquiry.

"The Chief of the Defence Force and the Chief of Army maintain their confidence in the leadership and actions of the members involved in this tragic incident," the statement said.

Mr Poate said he had "no confidence whatsoever" in the leadership involved in the killings, and that this Defence comment was contrary to the coroner's findings.

He said in the families' view Defence were also "as obstructive as possible" throughout the inquest and had argued national security concerns warranted the brief of evidence being kept confidential after the findings.

Defence said in their statement on Tuesday they had worked closely with all parties to ensure "as far as possible, the hearings were conducted in public".

Mr Poate said he was confident the highest command of the Defence Force would take notice of the "significant findings" by the independent umpire and implement measures to guard against the failures found.

Hekmatullah was captured in late 2013 and sentenced to death for the murders.