I agree that the AI has serious issues, but not in 39' as the OP stated.
In 43' I had my fun with the escort AI who will chase you (playing only with stock game, no moded AI), but soon as u dive under 50m.. they lost you. But, they camp the place pretty much time and drop a lot of DC's around the las contact area.
Not sure that the AI behavior is not hard coded as I tried few mods where the thermal layer effect was disabled and still the AI lost me under 50m. And thats with the gramophone and engines at max
TDW said that he is working on AI, finally somebody who work on the biggest problem in the game.. I'm really curious about his results...