It sounds like we want to drop the pd turret all together and considering you can shield up a ship with emitters that will do that job and more I can understand.
How ever the current pd missile relationship is based on a 50/50 kill chance, HP does not enter the picture. This is before coming into the other defenses.
Energy and ballistic weapons only have to contend with two defenses (armor and shields) while missiles must contend with three and considering how much slower missile weapons load this can be a problem.
To me missiles come across as either a support weapon or a bust weapon for overwhelming a ship completely. In the current build as a support weapon missiles are not great.
But this is about PDs so my thoughts on that are give the missile health and switch the PDs from ballistic to instant beam weapons and reduce range while at the same time allowing them to fire on enemies that are too close.
Finally I believe shields are too access about especially if you consider that the emitters cover a small area and missile don't focus fire. I do appreciate the concept, but and I know I throw my two cents out there alot but just hear me out. What if the shield generator was more of an internal unit with a larger room (4x4 or bigger) that covers more area and is an energy hog when deployed making shields more of an ablative armor rather than a solid end all defense.
The other rout is to make shields a damage damper.
Point is missiles have more defenses to go through so when they hit they should hurt a lot or be able to bypass other defenses like armor or something.