Just some rough numbers for anyone in the debate…
To bring Carmilla down below 90% HP it takes a move that would normally deal 5,000 damage to her (assuming there was no defence buff). To get her below 80% (where she can’t use vigor bloodfury) it’s 10,000 damage.
So that means normal critical moves can bring her outside the defence buff, but only the stronger ones. To take her outside vigor range it takes literally a blood move.
It should go without saying that it takes A LOT to actually stop her from simply using vigor bloodbite and then when you do, it’s 42TU to heal to 100% and require a blood move / multiple critical moves to counteract this 42TU. Carmilla’s aggression is not a problem nor is it reliant on rapid healing. The blood drain healing is way faster than it’s realistic to undo the health gained.
There are ways to kill Carmilla… payback killer, piercing or (more generally) a strong critical move followed by another critical move before she gets a turn. The 85TU she gives you for that last option is a bit tight and if you mess it up she’ll spam 42TU blood drain until you let her get another kill and give you a bigger window. This is the kind of situation the nerf requesters are talking about I think. 70TU on the blood drain move would make a lot of difference to that, without actually affecting Carmilla’s functionality or aggression.