I have just stumbled in to this thread and only have reviewed a few pages, so apologies in advance if the next comments have already been covered.
The ATSB have recently released their report:
https://www.atsb.gov.au/publications...-2012-154.aspx
It appears the engine failed because of lack oil. There is a suggestion there wasn't enough oil on board at the start of the trip (c.5 quarts instead of the 6-7 recommend). What was more surprising (in my view) is the plane flew for 2 1/2 hours after the oil light first went on. (In that someone would fly past so many ALAs rather than engine lasting that long.)
The pilot tried to solve the problem in the air by calling the maintenance centre. (Too many options perhaps?) Personally I would have favoured doing this safely on the ground.
Was the chute pull unnecessary? My view, I think the engine failure was unnecessary in the first place.