From what i heard and read, it was a dual hook long line set up...so three people hanging from the hook should be no problem for the helicopter.
Reading about downdraft and the load crashing into the rock, it wohld explain why the rope broke..the question is-what caused the height loss?
From all i read so far, there was nothing wrong with the system itself....
Three possible explanations i could come up with so far (guessing, of course):
-Pilots error
-Strong winds (leading to pilots error)
-line trapped (see above).
Really interested in the cause-might be some interesting "lessons learned" in there...