Gullibell
"...or are otherwise experienced pilots but with little PNG experience being caught out in unfamiliar conditions."
I believe you have it.
Over several years there have been several acidents like this one. To my observation there has been the recurring theme of pilots having accidents within their first or second tour (six I know of personally.)
There are probably many factors involved. It's usually a stressful time to begin any new job. Just coping with the new company personel and paperwork can distract from the flying. Throw in a radical cultural and geograhic change and what have you got? Stress. As you speculate in your post, the new pilots are expected to perform as well as the "old hands."
There is usually a lot of pressure from the operator to provide a seamless service to the client when a pilot leaves , but little resource is available to ease a 'newbie' in slowly. The cut-throat nature of the industry does not leave a margin for unproductive learning periods for these guys. Even attaining a work visa takes ages so the rush is on from day one.
The client can also put pressure on, even unwittingly. Some people involved around helicopters seem to become more expert in the operation of them than the pilots. They will judge a pilot purely on what they have seen others do before him. If you don't front up and perform to that standard you can be labelled unproductive by these dangerous people with little knowledge, big opinions and the ear of the management.
There are the usual obvious answers to fix these problems, such as take care of the experienced guys so they don't leave, have new staff on hand ready to be fed into the system slowly, but of course all remedies need money. Neither the client nor the operator will expend that in the name of safety. They would rather take the risk that the new guy can hack it. And of course many do. Sadly some don't.
Will it change? Don't hold your breath.