The thing is, that damage model on these ships works as it should. Different equipment takes damage, and crew is able to repair it. Its this hitpoint thing that is the culprit. In real life, lucky hit or a well placed shot even from smaller calibre can destroy, or at least cripple, much larger
targets.
But in this game you have to actually reduce the hitpoints to certain values to trigger a reaction. Just yesterday, while testing the Fiji in Tokyo-Saipan SP mission, my ship was pounding the light cruiser that was escorting it, and although it was full of holes and the deck was under water, it didnīt sink (and while in this state it was still in the process of making holes in my ship also).
So in order to make surface ships more realistic, the armor and shell system would have to be totally revamped, but as I understand it its the limitation of the engine, so there is not much that can be done about it.
Cdp44