Lance Corporal Neil Mackie and Private James Gosling hit out saying improvements that were made after the deaths of their colleagues should have been made sooner.
The men appeared at the joint inquest into the deaths of Corporal Andrew Roberts, 32, from Middlesbrough and Private Ratu Manasa Silibaravi, 31, who were killed by enemy mortar fire while inside the Forward Operating Base (FOB) Ouellette in the northern part of Nahr-e-Saraj district in Helmand province on May 4 last year.
The victims, attached to 1st Battalion The Royal Welsh Battlegroup, died from horrific injuries after the mortar crashed near a tented zone where the men had an outdoors 9am briefing on mental health.
Today, the inquest at Oxford Coroners Court heard the mortar - known as indirect fire (IDF) - smashed a crater into the ground 70cms wide and 30cms deep and sent soldiers flying.
L/cpl Mackie and Pt Gosling said fortifications around the base were insufficient.
L/cpl told the coroner Darren Salter that the FOB had previously been attacked by insurgents but after the men's deaths improvements were made which he was struck by when he returned to FOB Ouellette several months later.
"I can honestly say the developments that took place between that incident and seven months later were astounding - it should have happened earlier.
"The protection near the tented accommodation was unsatisfactory.
"The nearest hard cover was a fair distance away."
He said there was more Hesco barrier protection and higher walls upon his return.
"If the same incident happened again in the same location the difference would be unquantifiable," he said.
"Where the tented accommodation was there was much more hard covering and reinforcement but there were only two hard covered buildings when this happened."
Father-of-three Cpl Roberts and Pte Silibaravi, of Fiji, were pronounced dead at the military hospital shortly after being hit by mortar fragments.
They were not wearing protective body armour as the threat level was at its lowest - dress state one, meaning body armour only had to be near at hand.
But L/cpl Mackie said for days beforehand there had been talk of raising the level.
Previous IDF attacks had taken place before I arrived in March, he said.
"I wasn't too thrilled to be going, if I am honest."
Pte Gosling added that a sergeant major had visited after the men's deaths and said the protection was insufficient.
He said: 2I felt the protection at FOB Ouellette could have been to a higher standard...
"It is a shame it took an incident like that for something to be done."
The dead soldiers were both bomb disposal experts from the Royal Logistic Corps.
Cpl Roberts was on his second tour of Afghanistan and had served on operations in Bosnia and Iraq.
The Section Commander in 23 Pioneer Regiment was responsible for leading a team trying to detect improvised explosive devices in high-risk areas.
The inquest continues.