Touch of Malice's final bullet does not deal double damage in crucible. You deal 44 Damage to the body and 65 to the head. You deal VoC damage. You also lose HP for every shot you take. This makes you a lot more vulnerable to damage. One shot makes you vulnerable to a two shot headshot from Hand Cannons, for starters. At least one less shot out of an auto rifle, for another. ToM is a very risk/reward type of weapon. If you can't aim and your opponent is using ToM, you're gonna die, pretty fast. If you can, they die before they can get close to killing you.