The problem as Always are the battlecruisers. Schanhorst class had battleship level of armor. Hood had battleship level of gun. Yet... not "battleships".
The bottom line was that battlecruiser was anything that was crappier than a battleship in one area.
Yes, Schanhorst was really ugly bastard

, it was not true battleship and not true battle cruiser. But by my mind it must be in one "game-level" with Dunkerque/ Scharnhorst/ Renown(upgr)/ Kongo(upgr). Weaker than true battle cruiser Hood and stronger than Giulio Cesare (after upgr).
(And it is interesting - "Giulio Cesare" class was battleships "1-lvl", but after upgrade these 4 ships became true battle cruisers of "2-lvl" with big cannons, not slow speed and low armor
Ok so you want historical ships, but then you should also want historical build times, because even in the real world a carrier does not take 1 year to 2 years to build... it was more like 4 years, with 2 years being at full build speed (100% practical). All ships would need to doubled at least in build time to make them historical
Historicity in HoI should not kill gameplay!
Historicity in ship's stats is good, it make a more complete immersion in the atmosphere of 2WW, and good for gameplay.
But if ships will have too long time of construction it will be not good for gameplay. So it will be good if we will take ship's construction time not average, but minimal as possible in real history.
For example heavy Essex-class carriers builded very fast - in 1 year and 3 month. Ok, It's normal time for carrier construction in game.
It is important to understand why any ships sometimes were under construction a very long time. Because the construction has been idle! No money - stop construction! No supplies - stop construction! No parts and mechanisms - stop construction! New ideas and conceptions - new blueprints - stop construction! It is like do not give full IC for construction in HoI and give only 50% or 30% of IC

So we do not need make construction time in game as 3-5 years or 20(!) years, as it often was in reality. Gameplay is more important.
I am thinking the opening posters stats maybe has forgotten about torpedoes from light cruisers and destroyers is there preferred method of attack vs a capital ship, and a deadly threat at night and / or under cover with smoke screens. The sea attack of 1 / 2 for a destroyer flotilla in the table above seems laughably low to me. Real world example is the results Taffy 3 achieved at Leyte.
Plus main gun with effective radar plotting is a major multiplier of effectiveness than just considering gun caliber. Shots on target from an Iowa 25 to a Queen Elizabeth 20 in the table above - would be more like attack value of 25 to 10, in my non-expert view. Is this worth considering?
I do not tell how ship's stats must be implemented in HOI-4 and I dont know what sea battle mechanic will be in HoI-4

In my third table I showed only an example, how I implemented real ship's characteristics in HoI-2 model. May be it can implemented better! But most important - this implementing based on real ship's characteristics and not based on not correct princip "New ship-unit is better in ALL stats!"
All I want to tell, HoI-2 and HoI-3 ships stats did not based on real historical characteristics! Stats was taken from sky!
And I wish HoI-4 ship's stats and classes will be based on historical characteristics of real ships!
P/S/ 1-2 sea attack of destroyers in my table is anti-Zerg ban. Of course this is not historically implementing. But gameplay is more important

Especially in multiplayer games which I play. In HoI-2 sea battle mechanic low sea attack of destroyer is standart way to ban destroyer's Zerg-fleets.
I think the OP has neglected to include both armour layout, quality of the armour, gun/torpedo layout and fire control measures in his stat calculations. For example most allied warships had radar fire control by late war whereas the axis ships did not. Worked wonders for accuracy especially in night battles.
Our game named HoI, not "World Of Battleships"
So, depreciation of cannons, type of shells, the quality of shells, the quality of the explosives, the quality of the targeting system, artillery not main caliber, speed of fire, quality of the armour, qualification of ship's team and much other we can not take into account.
So it will be good if we will use only 4 key factors for correct realistic implementing of ships - main calibre, number of main calibre, thickness of Main armour and ship speed. Unfortunately, even these 4 key factors were not implementing correctly in previous HoI!
Torpedoes, Radars, AA and targeting systems can be attached "brigades", no problem!