Just found this nice little link, the perks deep freeze (frost spells paralyse when health is low) and disintegrate (shock spells insta kill enemies if health is low) affect the elemental cloaks.

So with frost cloak, whenever the enemy gets below 20% health they fall to the ground paralysed, and with lightning cloak they disintegrate.

I'm using elemental cloaks, and those will be my next perks in destruction.

I don't like the flames perk though - especially when you're trapping souls, "Come back bear!...too late "