The only cases where volatile has any sort of effect is when a volatile enemy is killed holding his teammates hands, they get tickled a little... and when an enemy heals mid engagement when the engagement was initiated with volatile. Otherwise, it takes too much damage to trigger a volatile explosion for it to matter at all. Its something that I dont even think about as voidwalker. Pocket singularity is just a ranged melee that can provide a little push on an enemy behind cover, but its countered relatively easily if used to try to stop a sliding ape, since the slide basically negates the push from the melee (as do sword swings or melee lunges).