Turrets have 1500 health, same as the Stalkers. It is actually possible to take them out without ancient arrows of parrying. For skyscanners, I like to find a cliff to jump off of and then jump right in front of them, then slow mo shoot them in the eye. If you need extra help, use a Lynel bow of the Eagle Bow (Revali's) to shoot three arrows (for the price of one) into the guardians face.