Nerfing PD tech further is ... problematic, since they are already (more and more) inferior to AMMs at higher tech. The issue here is full-sized launchers are ill suited for penetrating PD unless the whole PD mechanic changes. Not buffing or nerfing, but change the way it is right now, that either you have enough missiles, or not enough missiles. Full-sized launchers have their niche uses anyway so no need to buff them anyway...
I also think that nerfing PD is the wrong way to go, it would be pointless against large salvos. I think that finding more ways to utilize full size launchers would be better. As there still are areas where they are effective and finds use.
I wonder if it actually is such a bad idea that box and reduced size are king in ship to ship combat. You can combat it with a combination of PD, shields and AMM, so it is not impossible to fend off even with lower cost.
I think we should concentrate more on micro missiles being overly abusive as that cuts into beam territory where beam weapons should be king and not spamming micro ASM missiles. I think this is more of a game balance thing than anything else.
I think balancing the micro missile can be as simple as adjusting the way missile hit chance is calculated now.
Currently, missile hit chance is (100% hit speed)/(target speed)*(various bonuses) - ECM, which is different from the beam hit chance calculation. See where the problem is?
For example, let's assume a missile with 100% hit speed of 12kkm/s, and 20% tactical bonus. On the defending side, we have a ship travelling at 10kkm/s with a whopping ECM 6. Under the current formula, the missile's hit chance would be
12/10 * 1.2 - 0.6 = 0.84
That's also why I mentioned earlier, right now for missiles, AGI can substitute ECCM, as making the 100% hit speed higher can counter ECM under the current formula (which is not necessarily a bad thing in terms of variants of valid designs).
Since the ECM penalty is applied after all bonuses, and the bonuses can make the base hit chance above 100%, ECM is not as effective as it should be. If it were changed to something similar to the current beam hit chance, then it should look like:
(min(1 , 12/10) - 0.6) * 1.2 = 0.48
In this way, ECM has a much bigger role in the final hit chance, making missiles without ECCM suffer when against a target with ECM. This should limit the capability of ECCM-less micro missiles against ships, also limit the performance of ECCM-less AMMs against ECM-equipped ASMs.