So I tried to give superhuman a try and it seems like the mod is not really intended for it?
Alien subs shoot 3 frames faster for each difficulty level above veteran, so 6 frames faster on SH. The baseline reload time for fighter craft is already only 12 frames, so on SH they fire twice as fast as on veteran. This makes Barracudas and Morays completely helpless against them, and the game becomes unplayable.
Maybe either increase damage with reduced fire rate or give all XCOM subs some small amount of armor to make difficulty scaling more smooth?