Something has changed.

Spiral Torpedo III no longer reliably generates 1 Martial Spirit Shard on hits, like its tooltip states. It happens currently perhaps 50% of the time if one's lucky, and in fights like Kutum for example, it hardly ever happens at all. As you cannot use Spiral Torpedo on cooldown, you should be generating 1 Martial Spirit Shard every time you use the skill and hit an enemy (Just like the tooltip states). This indeed was the case up until recently.

Hopefully this bug can be fixed so it works again as intended.

The above bug also happens quite often against Ascendra and Kharoxia in the Pity of Undying.

It's now not just Spiral Torpedo, Rapid Stream is also not generating Martial Spirit Shards properly at times. Also the spirit shard generation is really tardy at times, sometimes you're through your next attack before the shard is added to the counter from the previous attack. 

For Spiral Torpedo, against multiple enemies is seems generally fine, the 1v1 enemies are where the problem occurs, it seems like we're almost too close to the enemy when we spiral through them, hit them multiple times, but no Spirit Shard is generated. 

Basically Mystic is practically efficiently unplayable like this. You can have the same rotation over and over again against an enemy like a guild boss for example, but each time it's generating different shard counts. Anyone that plays Mystic knows how important Martial Spirit Shards are to effectiveness.