We went up this past summer. We were doing fine until we hit a construction area just west of Whitehorse, when a big rig coming the other direction, well over the speed limit, showered us with stones. Our first ding in the windshield. Just after leaving a Kluane Lake campground, we came to the aptly named Destruction Bay area of the Alaska Highway, and once again an on-coming speeding big rig showered us with stones. Bigger ding in the windshield and many small dents in the skin of the RV.
There are two things to take from this: 1 initiate your defensive driving in these areas, staying well back from the vehicle in front, and stay as far to the right as possible, but keep in mind you can still get "hit" from oncoming traffic, and 2 we would do it again for the experiences. Remember, that the roads being disrupted due to frost heaves is real and on-going, and just part of the "dues" you may pay to visit Western Canada and Alaska.