Yay for announcing things before you have time to work on them.
I've had to pretty much scrap all the weapons I had before to get PD properly balanced. A 'default' PD gun is now rated to destroy a 'default' incoming missile 100% of the time..but just short of impact, and only if both are stationary. A second missile will ALWAYS overload the defense and impact.
This means charging a missile-firing unit is going to hurt, because even that first missile is going to hit now and then. Its also better balanced than it seems because most PD guns now cover only a single firing arc.