In battleship combat, unlike the old days of sailing ships, the guns were designed to arc the shells into the target and drop through (hence the term) the deck armor and superstructure armors.
They weren't designed to do this, so much as long ranges and muzzle velocities limited by by the speed of the expansion of burning powder forced them to. Because the deck was hit at a very acute angle by shells, deck armour could be only 1-2" thick and still resist enemy shells at realistic engagement ranges. 2000 lb AP bombs carried by late-war aircraft, on the other hand, were like a Lawn Dart through a paper boat.
The punching through the deck ship-killing method was why Billy Mitchell declared years before (and proved) that aircraft made the battlewagons obsolete. The Arizona, Bismark, YAmato...the list goes on, proved him right.
At the time - 1921 - he was wrong; the tests were more a propaganda exercise than a real test of battleship survivability. Also note that the
Bismarck was disabled by torpedo bombers, the
Yamato suffered a combination of bombs and torpedoes, and the Arizona was lost to a bomb that detonated her magazine that could not have penetrated her armour - either a hatch was left open, or powder was stored on deck. (Courtesy of Wikipedia; it's not like I carry my two
Conway's All The World's Fighting Ships with me all the time.) Early/mid-war battleships had more to fear from torpedo bombers than dive-bombers.
The heavy armor belts around the hulls of battleships were for torpedo defense, along with spaced armoring called torpedo bulges.
The heavy armour belts predated the locomotive torpedo, and were there to stop AP shells. Their anti-torpedo benefits were minor - damage from torpedoes came from shock and flooding, which an armour belt wouldn't stop. Certainly the difficulty and expense of sloping them wasn't justified by anti-torpedo benefits.
Now you could argue that that rule shows that fighters could do the same thing to a 100kt battleship in High Guard that planes did to the Yamato WW2 and always try to do the bomb runs in the areas where the batteries had been scrubbed off. The planes didn't sink the Yamato, but they got close enough to cripple her and she would have been easy pickings for any nearby battleship as a result.
They did, actually. She was listing, but was destroyed by a magazine explosion caused by a fire.
Maybe a torpedo run against a capital ship should somehow have it factored in that if the torpedo craft ( a large fighter with a missile bay sized nuke missile) approaches inside these damaged areas then it can get close enough to fire the nuke into a vulnerable area and damage the ship in a real way?
'Scrubbing' is an interesting idea; Wikipedia states that strafing caused casualties among the AA gun crews of the
Yamato, and while this isn't likely in
High Guard, the damage tables imply that weapons and fuel aren't fully protected by armour envelope.
High Guard also implies that fighters have a place in the fleet with the initiative roll. The larger fleet gains a bonus of +1, and every craft capable of moving and firing counts. That +1 can make a big difference if you're facing a meson- or missile-armed fleet (that is, almost always.)
--Devin