There is some sort of strategy I see.
Let's say you have 2 bays. You plan to fire 48 missiles towards the enemy. The enemy PD can stop 36 missiles.
If you fire 48 nuclear missiles, the enemy will stop 36, so only 12 will hit.
If you somehow overload his PD, (decoy missiles, multiwarhead or something else with a penalty to PD), he will use his 36 PD to stop only, let's say 24 missiles (the decoy salvo). So the full salvo of Nuclear missiles will be able to get close, optimizing the damage.
Of course, there is the question of how soon the enemy will realize they are firing PDs at decoys.