I'm not sure how you'd train to cope with anything that causes a stuck main rotor actuator.
I trained for stuck collective and it was manageable. Helicopters have a few more vulnerable lift, thrust and control elements than airplanes do. A lot of design consideration has gone into maximizing reliability, and creating compensating systems or flying techniques. Generally, they work, and if indeed, helicopters were flown like airplanes (avoiding hovering), more failures would be more manageable, but then it would kind of defeat the basis for choosing a helicopter for the role. Helicopter operations by their nature require accepting some additional operating risk, and vulnerability. For my experience, a main transmission driven tail rotor/fan provides the greatest opportunity to design out failure points and increase reliability.