Truck suspension changes will probably not help and they'd be a unusual solution I've not seen discussed here or on the trailer towing forums I frequent.
Trailer sway is primarily the result of improper weight and balance. Conventional trailers need at least 10% of the total trailer weight on the ball and 15% is often better. Hiloc has 12% and is still getting a little. I get none but, perhaps, my 10,000/1000 pound rated Equalizer (brand) WDH is handling it better. I've towed the same trailer, using the same WDH, behind both my former 2007 and current 2017 Expeditions.
I had a tire blow-out (not merely a flat tire, I thought someone hit me from behind!) at speed on the Ohio Turnpike 18 months ago and easily pulled to the shoulder for repair. I credit the WDH, the Ford trailer sway control (built into the Ford trailer brake system), and my "boss" driving skills.
Primary lesson learned in that incident: Don't tow with old tires on the trailer. Time flies and I had no recollection how old the tires were.
-- Chuck