It's the nature of the beast. I followed my friends in a brand new Pace Arrow on a 2,000 miles trip and all I saw for days out my windshield was that thing swaying from left to right and then watch it snap when corrected.
I've been behind the DP's and they all do it too. High, narrow, profile vehicle. Add any kind of wind and the swaying doubles.
The 'only' ones I don't see having this problem is the Prevost's etc. I.E. "Bus conversions". Greyhound wouldn't have gotten very far as a business transporting people if they used the MH chassis! :B