[Armistead]

The AI is based off numerous factors. Mods change values such as depth, cone, etc., of sonar or other equipment. Mods like TMO generally adjust equipment values. Then you have values that control the AI works that increase or decrease how the crews, environment and equipment sense you. Values are numerous, your speed, his speed, profile of sub, thermal layer, silent running, weather, visuals, etc. Then each enemy ship has a crew rating from poor to elite. Crew ratings are like multipliers for the other values, an elite crew basically gets a bonus added to numerous sensors. The env also comes into play based on the mod with it's numerous light values.

When you attack your goal is to stack as many values in your favor. If the values are highly in the enemies favor, you may want to track, even for days.
Simple, you don't want to attack a group with several escorts in dead calm seas in shallow water. If you can attack in rougher weather with waves and use silent running, they basically are deaf, even in TMO. Always keep a narrow profile to the nearest escort. You beat a mod like TMO with tactics. If you run RSRD with TMO, if basically only tones down the crew ratings, doesn't change sensors, except some equipment.

Learn tactics, once you do , even TMO will become simple and you can basically sink at will as long as you don't make dumb mistakes.