http://dbd.game/killswitch
Sole survivor buff
As more of your friends fall to the Killer, you become shrouded in isolation and less exposed to the killer.
For each killed or sacrificed Survivor you receive a token.
1 token: Your aura cannot be read by the Killer within a maximum range of 20/22/24 meters and your grunts of pain are reduced by 0/25/50%.
2 token: Your aura cannot be read by the Killer within a maximum range of 40/44/48 meters, your grunts of pain are reduced by 25/50/75% and your scratch marks disappear 1/2/3 seconds faster.
3 token: Your aura cannot be read by the Killer within a maximum range of 60/66/72 meters, your grunts of pain are reduced by 50/75/100% and your scratch marks disappear 4/5/6 seconds faster. You also don't leave pools of blood.
This way I think it would make the perk more usable on its own then to just have killer not see you if he has a perk to see you as if you are the last survivor isn't really usefull.