I ran a search regarding destructable torpedo threads... Some made suggestions about making them indestructable, but I think that the latter defeats the point of giving such torps slower projectile speeds. However, simply making them "vanish" upon being hit also doesn't make much sense either... After all, what normally happens when you shoot at an armed warhead? The answer: armed warheads will usually detonate when they hit a target or are hit by enemy weapon fire.
From a canon perspective, STO destructable torpedoes should follow the above principle as well. Energy weapons which successfully hit destructable torpedoes should normally cause premature warhead detonation. Other factors like critical hits or phaser and polaron weapon procs could neutralize warhead triggers, but this should not occur 100% of the time like it does now. To summarize, I suggest that destructable torpedoes detonate when they suffer normal energy weapon hits. However, if they sustain a critical hit or phaser/polaron proc-hit, then they should just vanish like they do now
Destructable torpdoes should also have a 10km maximum travel distance, then automatically detonate once they reach this limit. UPDATE: This suggestion isn't needed from a pvp perspective. Scratch this idea.
Lastly, since explosions are not supposed to be selective, perhaps heavy torpedoes like Tricobalts should be changed to deal damage to all nearby targets (to discourage point-blank TCD launches). UPDATE: scratch this suggestion as well... Too mant logistics issues! :p
Everthing else above should still be OK.
All thoughts/suggestions/comments are welcomed.