Does anyone else get the feeling that base hit points are too high, and attack-specific defenses are too low?
I get the idea behind the defenses-as-additional-hitpoints mechanic, and it's not a bad one - it's more straightforward than the modifier approach in GC2, and it makes ships a bit tougher against attacks they're built to withstand. But, as has been pointed out, it's generally better to ignore defenses altogether and just use as many weapons as possible. Most ships have enough tank to survive the firepower of a 'generalist' boat, while a generalist boat will not have enough tank to survive the firepower of a 100% beam/missile/gun ship, as his defense value won't cover the shortfall. Even though defense hit points are regenerated after every battle, they're still not valuable enough, because they cannot counter the full force of an attack.
I think that reducing 'structural' hip points by 50%, and increasing 'defense' hit points by 100% would fix this. A heavy PD boat would be able to withstand alpha strikes from missile boats, and would be able to take out a defense-free hull in the return salvo. Picking weapons to circumvent the enemy's defense tech would suddenly become important again, rather than just massively outweighing the def value with extra guns.
The basic hit points of a ship should basically account for the few millimetres of hull between the crew and outer space. Everything else is accounted for by armour, shields or PD. Anything getting through those should cause grievous damage to any ship, no matter the size. We shouldn't be seeing hulls with 5-6 times the basic tank of their defense mods, which currently is the default.