in real life no captain will go after the DDs - too dangerous and the torpedoes are too precious for these small ships... But to shoot the biggest ships and then try to hide from 4 angry DDs (not the game default ones, but the tweaked ones) - that's the fun
Also I don't see the point of shooting the decoy after you kill the first DD... Looks like you're cheating the system (game)...
Not that "cheating" is wrong (otherwise I wouldn't create
KillerSub mod)...