Standing in the crowd at a rally calling for a royal commission into the Department of Veterans' Affairs were the parents of Jason Grant, a veteran of Afghanistan who died of a suspected drug overdose at his Ferny Creek home just a month ago.

Ross Grant was a quiet but powerful presence at the rally on Tuesday, holding a placard reading "DVA Killed My Son" as well as photos of Jason in uniform, in recent years and also as a child. 

Although still reeling from the death of their son at the age of 32, Mr Grant and his ex-wife, Lisha​ Taylor, joined the call for a royal commission into a "broken" Department of Veterans' Affairs.

Veterans' advocate Mick Quinn, the MC for the event outside the department's Melbourne office in La Trobe Street, said it was also a memorial service for the 56 Australian veterans who have taken their lives this year.

He said the "adversarial manner" many veterans encounter at DVA is exacerbating the strain on already severely stressed people.

On July 11, Ms Taylor found Jason dead on the porch of his house in Melbourne's outer east.

Jason served two tours of Afghanistan over nine years, from 2004.

In 2011, in Oruzgan province, his mate was shot through the neck and killed.

Eight days later, Jason killed a Taliban fighter who had shot him in the shoulder strap. Ms Taylor said Jason asked for counselling but was advised to "harden the f--- up and get on with it". 

On return to Australia, Jason was diagnosed with post-traumatic stress disorder, and medically discharged from the army four years ago. He lived with his mother, and suffered depression, anxiety and a back injury. 

A coroner will rule on the cause of his death, but Ms Taylor suspects an accidental drug overdose. Jason had been experimenting with drugs, and drinking, to alleviate night terrors.

Jason also waged a diabolical battle for government entitlements.

Ross Grant said: "He was suffocated in paper work. Bureaucratic bungling and lost files. They kept changing his case officers. He was already stressed and anxious. It plunged him into depths of depression." 

Ms Taylor says the department made him go from doctor to doctor to prove worthiness for compensation, most recently for his PTSD. Last November, he reached 49 of the 50 points needed, so he didn't get it, leading to severe depression.

Jason was on a TPI (totally and permanently incapacity) pension, but had a portion of it – for being in a unit attached to the SAS – reduced.

Ms Taylor said a royal commission would hopefully remedy the DVA's "ridiculous" bureaucracy.

"It's just desk shuffling and no one seems to care," she said. 

"They need one specific case manager to follow their story from start to finish.

"Jason would still be with us now if that was the case."

Last week, a Senate committee recommended the government commission an independent study into the mental health impacts of the claims processes. It said many witnesses' testimonies that the claims process is a key stressor and a contributor to suicide should be examined. 

Veterans' Affairs Minister Dan Tehan welcomed the findings, saying major reforms had been made including making mental health treatment free for ex-soldiers, and upgrading IT systems to reduce claims processing times.