In his second season back with the Warriors after three years at the Sharks, Johnson turned the clock back the golden days of 2014 when he collected the Golden Boot as the world's best player.
The home side got off to a flyer in the sixth minute when Johnson produced a superb solo try from close range, leaving Dolphins skipper Jesse Bromwich in his wake with slick footwork.
The Warriors threatened to go further ahead in the 11th minute but some desperation defence by Euan Aitken around the legs and Tesi Niu up high denied Charnze Nicoll-Klokstad.