A main rotor blade strike does a lot of very bad things to the aircraft in flight. First, the initial impact, significant enough to cause structural failure of that blade, stresses everything from the point of impact to the power plant. There's typically something like 20 times the amount of useful lift in centrifugal force in the MR blades. the event would create an imbalance that could affect the aircraft dramatically. Off the top of my head, the last issue would be a difference in lift by the airfoil involved when it's "inadvertently de-optimized" by the event. That difference in lift also creates it's own imbalance as the blades doesn't flex as before and is now further out of phase.
Catastrophic structural failures, like the tail boom separating in this video, is pretty typical of this kind of event.