I do a lot of shooting of old military rifles and live in Alaska. Sectional density and penetrating power are always big topics of discussion when it comes to Bears.....
I think you are correct that Bismark and Tirpitz were not designed as commerce raiders. Essentially sea superiority vessles in the traditions of the High Seas Fleet. Perhaps Graf Spee etc could be considered more commerce raider designs. The piecemeal dribbling out of the German Heavy ships without viable air support was a vast waste of resources. A concentration of resources would have participated a serious issue indeed for the Royal Navy and possibly her cheering section.
Indeed Alaska's super heavy shells, for their caliber, were potentially very effective on armor. However her own armor would not have permitted reliable protection against ships significantly larger than cruiser size. Magnificent steamers and beautiful in form, but a battle cruiser in effect with the limitations of that type. Amazingly for a USN type, the mechanicals of the turrets did have some "issues".
The superheavy 16" shells fired by the lightweight 16:50 of the Iowa's were probably equal to the Yamato 18" in penetration because of their high sectional denesity. It is amazing however to note that the USN had no real idea of the size and especially armament of the Yamato etc till after the war! The Island Empire was pretty good at keeping their secrets!
Bismark's high velocity rifles made some sense in the North Atlantic, especially before Radar became sophisticated, as combat ranges were not expected to be extremely long due to the prevailing visibilities. It is believed that Dorsetshire destroyed Bismark's main fire control station early in the final engagement, greatly reducing her effectiveness after a few early stradles on Rodney. Not everything can be protected against large caliber shell fire, as witnessed by the reduction in combat effectiveness at Guadalcanal of SODAK from a great number of mixed caliber hits, none of which penetrated the armored parts of the ship. She was lucky to have Washington, an effective ship, as a backup!
Lastly, the figures I remember for barrel life for full velocity charges for the USN ships was not greatly over 100 rounds. The famous Paris Gun of WWI had shells of graduated size, to be fired in order!
Cheers: T