Ok, my previous train of thought is finally approaching the station. But first, thanks to those who have been making the observation for explaining the to-hit nonsense for mobs that can't move. This makes no sense. They could at least allow auto-hit, or a significant AC penalty, without the auto-crit. But if it works both ways, I won't complain when I eventually run an AC tank who is barely touched while held.
Turn PA on when you have to roll a 20 to hit anyway. If you're that far under level/geared that you're only hitting 5% of the time, you might as well hit harder when you do...