Was carrying spare torpedoes on deck worth the risk?
Short answerThey added risk if the ship was hit, but the extra torpedoes were judged useful enough to justify it.
NotesA heavy hit already posed a serious danger to a destroyer. Spare torpedoes on deck increased that risk, yet also provided additional weapons after the loaded tubes had been fired. The extra offensive capacity is judged worth that additional danger. This is a preference about accepting risk in battle, rather than a claim that deck-carried torpedoes were harmless.