You don't need to blind them, they are running away everytime you cripple them, when I was playing for unarmed (or melee) I was always hitting legs, afte rbreaking leg they starting to run away from you on few hexes, so you can hit them again and again, blinding is good only against NPCs that don't flee when crippled. You can easily kill pack of deathclaws by crippling thier legs one by one and then simply chase them over encounter map to finish, when they are close to exit grid overrun them to be between him and exit grid so he'll start to flee in other direction.