Thomas:
The company I work for practices double engine failures in the sim on all our helicopters every 6 months. 139, 225, 76, 92 ect. In pre sim days we practiced them to a power recovery at least once a year in the 212 and 76.
One must remember that a tail rotor failure can also lead to a dual engine shutdown.
In any case the rule in any type be it single or twin should be to lower / raise collective as required to maintain RPM in the green. If that is all you have time to do is that then that is the first and only priority. No RPM = a very bad outcome.
I have followed this thread since it's tragic beginning and have no idea or theory as to what happened.
In single engine times we practiced "full on" outos in 204s, 205s, 206s all models, 350s, 500s and, dare I speak of them, 47s every year. We never bent a machine in practice. Perhaps we were just lucky in having great training pilots.