[Alneyan]

I believe the problem isn't that PDC is too strong(*), but fighters are too weak, and, more specifically, have a very hard defence vs damage balance. Those fighters are also expensive (particularly to research to high levels), and logistics for are a nightmare. Since you must gather thousands of them in any serious battle, getting enough Fighter Bays to do that is going to be tough. They make a very nice defence taskforce when set at a wormhole ward, though.

* PDC has a mere 3.5 damage ratio (damage/kt), where most other weapons are around the 1.5/2 mark, and aren't restricted in their targetting. PDC cannot be mounted, unlike those other weapons, so a heavy-mounted APB XII deals exactly as much damage per kt as PDC, and is always useful. PDC does get a +70 bonus to targetting however, whereas a ship will standard training and components will only fire at 65% accuracy. I am assuming the fighters are in a fleet of their own (seems reasonable enough), but that they also have ECM III: that seems less likely, given how much research is needed for those things.

So yeah, PDC is very strong when you don't have anything else, but I think it is pretty much balanced in the middle game: it is better than the APB at taking down fighters, but it doesn't do anything against ships. Seems fair enough to me.