Guys, the issue of leaving a machine rotors running has been discussed extensively in
Leaving helicopter with engine/rotors running. Under Australian regs we are allowed to do so under certain conditions, and many of us would say that if done properly it is both safe and is essential to a remote operation.
I've operated a Wessex 60 offshore single pilot where it would have been foolhardy to have shut down both engines whilst refueling (so I and others would leave one running) on a coral atoll with no backup should a battery start fail. I've operated an AS350 in Antarctica where the fuel control cable was frozen and a restart wasn't guaranteed, necessitating constant operation all day without shutting down. Even pulling back to ground idle was a task. What other option was there other than careful calculation of the risk and the demands of the operation?
As another poster stated earlier, I don't subscribe to turning off the hydraulics as an aid to locking the controls. A proper control lock as in the BK117 or a well maintained and effective control friction is essential, plus skid gear. That and a justifiable requirement to exit rotors running are my criteria.
As to why the pilot left the machine in this accident, I think the NTSB initial report is too vague for us to be making judgement. Those who operate in regimes where rotor running exits are prohibited, you may benefit from viewing this from the experience of others who are familiar with the concept and use it on a regular basis instead of condemning the practice out of hand.