About FFG passive sonar not detecting torpedos - we didn't changed it at all. Only reason could be lower NL of torpedos. I tried to calculate torpedo base NL and noise curves so to get unchanged original NL as a result, but maybe I made a mistake somewhere, I'll check it !
About AI sub doctrines. We didn't change it at all beside little fixes of miscalculated ft/m depth settings and added AI reaction if it detects underwater missile launch (reaction is set same as for enemy torpedo launch). Yeah, default doctrines are very basic, I said it few times already, ans MUCH can be done. But it's a lot of work and later testing if all works correctly, I have little time lately, maybe now I find some to further improve 1.02 and maybe add some new already tested stuff (like custom ADCAP and UGST doctrines).
Maybe try to modify the default sub doctrine ? The language is really simple, only you have to paid attention to things like spaces, { and so on. Jsteed's descriptions and his tools to check doctrine integrity (SCDoctrineChecker and doctrine language templates for EditPlus text editor) is all I had and all my knowledge about doctrines comes from.
Later you have to test doctrine with DbgView active to check how it works, it's good to add custom debug comunicates (Debugout, DebugValueOut) after each more important command in test phase and delete them in final version of doctrine.
And finally, IIRC in SCX the AI behaviour doctrines (for example torpedo evasion) were in fact much improved and it made a distinct difference, maybe importing some SCX doctrines into our mod would be good idea, they are ready and very well tested. Much of my work was inspired by SCX doctrines and database solutions, I even used parts of them for example in my ADCAP torpedo doctrine doctrine, but up today I never used complete SCX doctrines. I know that great amount of work was needed to develop and test them. Anyone know who I should ask for permission use them in our mod ? Or maybe it would be OK just to use them with original headers and mention use of SCX stuff in mod documentation ?