I don't think we can rush to judge. Mental health is a long game. It has many steps, and the 'suing for compensation' step is wayyy down the line. Usually a court or other arbitration method won't enter into discussion of suitable compensation until the condition is treated and stabilised.
The usual path includes:
Injury (which in the case of mental health can take months to manifest into something recognisable that you seek help for).
Medical attention - initially a GP is sought (although in some workplace cases, where they have counsellors involved, this step may be skipped
Referral - The GP or Counsellor makes recommendations that the person be referred to a more qualified person - usually psychiatrist \ psychologist.
The specialist assesses the person. At some stage between GP and this step, a medical opinion is made, determining whether the injury is work related, and if so, a workcover medical certificate is issued to provide the employer.
The specialist recommends treatment - this can include counselling, medication, adjustments to duties etc.
The workplace HR machine switches into action on receipt of the workcover certificate. Either a dedicated HR person, or a contracted 'rehab consultant' is involved to manage the case. The employer's workers compensation insurer is notified of the injury and their team gets involved too.
The insurer or relevant party needs to determine whether the claim is compensable - is it genuinely work related. They may require the worker to attend different ("independent") doctors or specialists to validate the opinions of the treating practitioners. Until this happens, the worker is usually having to manage their condition using their own entitlements for sick leave etc, although some employers may allow use of 'special' leave arrangements so that the worker isn't out of pocket during diagnosis prior to the claim being accepted.
If the insurer accepts the claim, they take over responsibility for costs. Some doctors won't provide treatment or assessment for a workers compensation case without upfront payment - something most insurers won't do until they've agreed to accept liability. This can make it hard for the worker to get the treatment they need whilst their income is depressed from taking time off \ exhausting leave etc.
The case manager will work with the insurer, the doctors, and the worker to determine what work the worker can do, what adjustments are needed, or alternate duties while treatment continues. This is ongoing from the moment the workcover certificate is issued, and the goal of the insurer, workplace etc, is to have the worker continue to work 'as normally as they can' whilst the case progresses. If all the doctors in this case were satisfied that the worker could continue to perform some, or all of their duties at Dreamworld whilst the case progressed, he would be obligated to do so with whatever adjustments to duties they felt were appropriate. This involves the worker in these discussions, so a bit of negotiation happens here - ultimately though, if he can work, then he is required to do so.
When the medical experts, including the treating doctor and the insurer's medical team are satisfied that further treatment is unlikely to improve the current situation, they determine that the injury is stabilised. At this point, the lasting effects of the original injury can be quantified - what impact has this injury had on the worker's career - what can they no longer do? what effect does this have on their ability to generate the level of income they had prior to the injury?
This is the point where a level of lump sum compensation can be determined. It is almost certain (my opinion only) that the insurer made an out of court settlement offer as soon as the stabilisation determination was made. It was almost certainly low-balled, and any halfway-sane person would have sought legal representation to advise them. Their legal advisor would have advised them to decline the settlement offer, and the next step is to lodge a case through the courts.
This guy hasn't sat on his laurels for four years. He's probably been through hell in this time. And while it has affected him, the affects probably weren't something that would prevent him from his duties.
I personally think that anyone who thinks the delay in lodging this claim is unreasonable probably hasn't been through the compensation claim machine for themselves, and has no idea what they are talking about.