The way I would think of doing it would be to have the interceptors move towards the target and once they've attacked, have them move into a circle, either to their left or right. Then you randomise the angle they have to travel until they have to either move into a straight line, or perform another almost-circle. Continue this until it's time for them to attack again, then angle their trajectory towards the target, and order them to attack again. If the distance from the target and the interceptor becomes too great, have them swerve back towards the target.