I agree I have a work truck 4.3L and my personal truck - work truck has 61+K on it now and has never vibrated - I had another truck besides the one I currently have they went through drive shafts, axles, wheels and tires and no fix so they traded me out. Now the one I have now had similar vibrations and I let air from the tires and it seems to have helped but still I believe there is a common issue or a manufacturing miscue that is causing this. GM should step up to the plate and not let this become a litigious point in a company that is already in hot water over trying to push things under the rug. The mere fact they are sending engineers and buying back trucks is enough to know there is an issue.
Oh and I have owned plenty of trucks to know how they drive. I have a one ton that does not vibrate and it has currently over 1.6 million showing on the odometer and the diesel and it have aging issues but not weird vibrations. Sort of sad I traded a perfectly good personal truck in on 14 when the 13 was just fine.