Macarthur Job's "Air Disaster" series deals with this accident and I would recommend it to anyone wanting to find out more.
In it, there is a sequence of photos shot from a RNZAF Iroquois which was carrying Justice Mahon as they retraced the flight path of the DC-10. By some uncanny quirk, a sector whiteout formed just as the chopper approached Erebus, completely obscuring the mountain and providing an extraodinary illustration of the phenomena.
It is quite easy to see from the photos how the crew thought they were flying in VMC conditions with unlimited visibility.
25 years on, I am not sure if the blame game is appropriate. Maybe the educational lessons for us all are a more valid aspect to take on.