GWX has simulated AI Wolfpacks. The burning/damaged escorts are still searching/engaging the AI Subs. If they have sustained enough damage, they will sink. Due to the limitation of SH3's code I would imagine that sensors will remain unaffected. As for weaponary, sure, this can be affected. It's good fun to destroy an escorts gun placements from distance, this will leave them toothless while you're on the surface.
The sound affects you heard from the Tanker were due to flooding compartments, bulkheads under strain and hull creaks. You will be able to tell the difference in sound when a ship is sinking.
