I've been following this topic for a couple of years.
Try looking
here for some clues.
In real life target depth measurement was largely guesswork until near the end of the war. Going very deep really did give a very high degree of protection throughout the war. Following the introduction of support groups in mid 1943 if hundreds of charges did not do the trick the tactic was to wait above the target for 24 hours, when it would have to come back up due to lack of battery or air. Escorts do not have this kind of patience in game and if you can avoid detection for about 20 minutes they will go away. 24 hour hunts are not good gaming material.
A related problem with GWX is that the charges are super accurate in depth and you can dodge them by going up or down by 20m when the escort starts its run. To be honest just about everything about the escorts' sensors is messed up in GWX! Not really the modders fault, it's partly due to mistakes in the base game.
I think the best thing to do would be to drastically
downgrade the charge depth accuracy by modding the depth_precision parameter in Silent 3ditor. This should negate the depth change tactic and also lead to a few exploding deeper. Not tried this, it might cause escorts to sink themselves when they make shallow attacks.
HOWEVER:
The game to some extent relies on the player's extremely poor ability to see what is going on. This is what gives the game its outstanding "feel" and where later games like uboat get it wrong. It also hides some dodgy simulation and extremely poor AI! The more you find out the more problems you find...