You need to watch a few films of the Starship Enterprise under the command of Capt. James T. Kirk. Forty years ago my generation didn't have any problems with electronic countermeasures. Watch this video from You Tube
YouTube - Destroyer Gets Destroyed By Submarine Torpedoes
Notice what happened to the radar, and how useless it was against the torpedo. No amount of armor is going to defend that destroyer after her back is broken by the torpedo. Ain't it better to think in terms of electronic countermeasures, fool the torpedo to think you are 200 yards away?