The problem with the PK was first and foremost the system (Tmac's fault), second the goal-tending, and a distant third the personnel. I honestly don't care who you stick in goal or on the D, that system was doomed to fail. I admit, Niemi isn't stellar on the PK, but he's serviceable (as shown by the Hawks). The Hawks employed an aggressive (on the puck) system that allowed them to win races to the rebounds and pressure the puck carriers. We did almost exactly the opposite and got the expected results.
That is Tmac's fault. Even if one of the assistants designed the system, Tmac still allowed it to be implemented and stuck with it for two freaking season. If you don't want him fired, fine, but to say he isn't responsible is pretty disingenuous. If Tmac understands penalty killing strategy so poorly that he needs to hire a new assistant to 'teach' him how to do it then that is a serious problem. Also, that person better be a PK Guru, not Arniel.