[ Doesn't help that most of those terms are in fantasy-russian, but they are a military organization, so it's not too hard to guess why they'd want someone that dangerous on their side. ]

Kind of. Heartrenders and healers are the same kind of grisha, just one specializes in dealing damage while the other works on repairing it. I had a friend back home who was a heartrender, she could put people to sleep with just a flick of her wrist. I don't know if it works by lowering your pulse or if she can target other organs specifically though, I didn't go to school for this like she did.