Left passenger wheel shakes badly

My passenger door seat is indicating a bad shaking problem with my truck. A mechanic said he replaced all tires and it still shook. I do not believe him because he later diagnosed a out of round disc but it still shakes. I had a new set of Michelin's installed when the problem started, but they put a new set on and still the shaking occurs. I had a new set of plugs installed and I have not mentioned to anyone that maybe a wire got crossed, after having the wheels rotated after an oil change. I had to have the wheels re-balanced because it shook so bad. Feel it is definitely in the tires or suspension. Ny suggestions?