Also related to scaling, for large missile launchers reload times are getting ridiculous. The same is for larger beam weapons, damage is proportional to power, and power recharge is directly capacitor tech, so power and therefore damage per HS drops off very quickly. Larger installations should be able to draw more power per piece even if not per HS.
It's fairly similar to how real weapons work.
A battleship main gun fired maximum twice every minute, alot slower in practice. But a Destroyer gun can fire more then 10 times as fast.
Basically a smaller gun can fire it's own weight in shells in less then half the time.
The advantage from bigger guns is the extra range that means a chance to fire when the enemy can't fire back at all, and for missiles the shock damage and more effective engines ( extra range ).