Nothing wrong with your mods list.
Nevertheless, you could update your IRAI to latest v0039 and its patch.
While i got very interesting fights and depth charges in SH4 lately, i had lot more trouble surviving SH5 destroyers with stock IRAI...
Had to tweek it down a bit to give me a little chance!
But i agree SH4 AIs are still VERY good and well made (using TMO for me).