I'll piggy back low light level players thru a raid all day. It makes them better. Makes you better. And helps them level their character up. Did you try switching his position? Having him hang back? Take an easier roll? Thoroughly explain what his job is and make sure he understood? All plays a big factor in a low levels ability to make sure you clear an area. The more helpful and friendly you are while giving positive feedback the easier its going to be for everyone. Hell. He might even learn a thing or two.