To Ascend Charlie,
The horizontal stabilizer on the N2/N3, is made of one block of very thin carbon fiber and there is no difference in pitch setting along its span to counterbalance the "effect of low tail rotor" (not even on other helicopter types I know)
Once again this inflight left stabilizer rupture already happened to myself and some others. In my case despite your theory, I barely noticed a difference (just a few oscillations in pitch and nothing in roll) although I was nearing the vne.
To crab,
I agree that given the circumstances, the hydraulic leak was more likely due to a torn off brake block. But a leak on this emergency reservoir also happened at several occasions (not under strain but typically from the weldings) Both of these leaks may dump something like 2 liters of hydraulic fluid or slightly more.
I'm just wondering wether the sudden initial and brief nose down after the loss of the left half stabilizer did not initiate an aerodynamic stall (sudden increase of the angle of attack on the upper surface) This aerodynamic stall would suddenly have cut the remaining downward lift and greatly amplified the nose down motion.