Graviman,
No it really doesn't double, since we use redundancy to control the failure rate to very low numbers. The definition of a flight critical component is that if the component fails, the aircraft has a high probability of a mishap. With a dual hydraulic system, the probabilities of a dual failure are very low, so they are not necessarily flight critical.
Usually, as the helo gets more complex, the number of critical parts drops, as a result.