So you're not convinced!
OK, let's argue on this:
Kanaris wrote:
I don't see any valid reason why destroyers should gain such a big defensive advantage in ship to ship fighting. That was not their role
For ships something like "defending" doesn't exist - on the open sea there were no positions you might want to hold and no shelter you could use. So what the attack and defense values represent are the ability of the ships to fight at distance or in close combat:
* To fight at distance, CoW ships use only their attack value, so the attack value represents the primary naval artillery of the ship => battleships must have a very high attack value, cruisers a medium one and destroyers a low one.
* Fighting in close combat is represented in CoW by melee battle, for which CoW ships use both their attack and defense value. Here the attack value still represents the primary artillery, since it can be used at short distance as well. While the defense value represents weapons that could be used only at short range (torpedoes and secondary, low calibre artillery), as well as speed cause it helps to escape torpedoes. So battleships should have a very low defense value, cruisers a medium one and destroyers a high one.
Kanaris wrote:
Using Destroyers for torpedo runs was the exception not the rule as more often than not they would get destroyed before getting within torpedo range so it was a tactic only used in desperation.
If we're talking about battles fought during WW2, you're right that torpedoes launched by (overseas) ships were seldomly seen. But that's because the fleet of the Allies was so overwhelmingly superior that Germany & Italy never and Japan only during the first year dared to attack it face to face - Germany totally focused on Subs against convois and Japan on carrier-based planes.
Anyhow this doesn't mean that WW2 destroyers weren't capable of fighting taller ships with torpedoes. They even were designed primarily for that. Are you saying they carried all these torpedoes just for decoration? No, whenever two fleets met, always the destroyers approached close enough to use their torpedoes. Take for example battle of the Java Sea (--> Wikipedia link <--).
Or let's look for example at the American "Later Fletcher" class, 62 ships of that type were built 1942 to 1944:
Artillery: 5 x 12,7-cm guns - with that they couldn't even tickle a battleship or heavy cruiser.
Torpedo tubes: 12 x 53,3-cm - that's heavy; that was a lot.
Now you said there was no need to change anything about Navy. But in my opinion, naval battles are very one-dimensional. You move your fleet within fire range and that's it - bigger fleet wins. My change would open several tactics: Fire duel at range / engaging at close combat with only your destroyers / engaging at close combat with both your destroyers and cruisers. And it would become a question in which formation you position your ships: Placing your destroyers and/or cruisers ahead of your battleships leaves the latter vulnerable against air, but having all in one stack makes it vulnerable to enemy destroyers engaging it in melee combat, while enemy battleships and/or cruisers stand behind and fire at range.
More importantly my proposal would make it more reasonable to build destroyers, cruisers and (optionally) battleships, which every nation did in real life, but which currently never makes sense in CoW.