"110 kts, straight and level, collective bottomed, 500 lbs below max gross, descent off the top of the mountain - wind sheer, a/s up to 155kts, a/c snapped to the right 90 degrees."
So you exceeded the max autorotation "collective bottomed" airspeed by 40 knots at sea level and it's a design flaw? Sounds to me like you put the aircraft far out of any reasonable design reserve.