From: Houston, TX
Rating naval units can get extremely complicated very quickly. So many variables, so many factors to consider.
Let's take one example. Gun power. To calculate gun power you need: rounds of ammo carried per gun, shell penetration data (both horizontal and vertical) for a spectrum of combat ranges, rate of fire (not at important as you might think), type of fire control (centralized? non-centralized? etc.), type of range finding (radar? stereoscopic? etc.), shell weight, crew training and experience, firing arcs (mounted on centerline? other?), and probably some other data that I can't think of off the top of my head.
Crew training and experience would be modeled by the unit proficiency. For the other factors, remember that TOAW doesn't actually simulate the launch of shells, their flight to the target, and their impact on the target. It just has an AP value. That's going to be more or less relative.
Then, once you have gathered the data you need, you then must create formulae that work. This is very difficult. For instance, I mentioned above that rate of fire isn't as important as you might think. Why not? Because it takes a certain amount of time for a shell to travel to its target (a shell that has an initial muzzle velocity of 2500mps might take nearly a minute, or more, to travel 30,000m due to the ballistic curve it follows to get to the target (it's not traveling in a straight line at a constant speed)). Then it takes time to analyze the results of the salvo. Then it takes time to make corrections for the next salvo.
All that is done with multiple shells in the air. They don't just fire one shell, wait for it to land, calculate the corrections, and only then launch the next shell. They fire more or less as fast as they can and keep track of all the shells - many of which are from different guns and even different ordinances.
Then, depending on the type of fire control used, it takes time to order and execute the next salvo. Thus, for example, even if a big gun has a rate of fire of, say, 2 rounds per minute, that rate of fire is never practically achieved in combat. Indeed, a well-trained and experienced crew might be doing good to get off a salvo every 90 seconds (at 30,000m) instead of the 30 seconds (2 rounds per minute) that the gun is theoretically capable of. And this means that simply taking 2 rounds per minute and applying that to a gun-power formula without any modifications (as described above) is going to produce gun-power ratings far greater than what the gun could effectively achieve in actual combat. And this is just one relatively simple example.
I expect that the values in WitP were effective rates, not some theoretical maximum. Regardless it would be true for all guns, so the relative values will be more or less right. Again, TOAW isn't simulating shell flight & etc.