I've always figured, if both truck and trailer are level, it's setup correctly.
If the TV is rear low, needs fixing by a WD, beefier and/or springs so the rear does not sag as much.
Also, if I can't tow the trailer at 60mph without sway, then I need to figure out the cause of the sway before adding the Peterbilt bandaid in my book to stop sway.
I could go on about more things too.
I've only used a WD on my RV trailer. The other half dozen trailers I've owned, or add a few dozen more rented, have all been dead wieght towed
Marty