Sounds to me like they were adjusted wrong.
Not sounds like.... They absolutely were.
Lets go to school guys.
The WDH, if set properly, will still allow MORE down pressure on the rear tires than when unloaded, but also will transfer some of that added down pressure (tongue weight) to the front axle for more steering control and more vehicle stability.
A good general/laymans rule of thumb is to measure your hitch bar and adjust your WDH so that your getting around 1" of hitch drop with a proper 10%-15% tongue weight applied. Obviously if you have a 2,000 lb trailer and 200-250 lb of tongue weight... a WDH is going to actually lift the rear end because you simply do not have enough tongue weight to make use of a WDH, and this can/will cause an unsafe condition with higher chance of the rear axle trying to pass you in a turn. This is where (not so)Common Sense comes in to play.
On a half ton truck especially, the rear axle gross weight is VERY limited. This can be seen in the vehicles advertised payload. Take my Max-Tow equipped 2017 Ram 1500, my payload is 1640 lbs.So with a WDH properly adjusted you are moving a portion of that load to the front axle and this puts the rear axle into legal territory while being much further into a heavy load and it makes the overall vehicle safer because..... Putting that 11,500 bumper pull trailer on your new Ford Eco-Boom truck with a 13,000 WDH assisted towing capacity makes that 5,600 truck gain weight in the right places so as to pretend that it is a SuperDuty. Without it, the trailer hitch is smashing the rear axle far past design limits and it is actually LIFTING (see-sawing on the rear axle, the fat kid is the trailer and he is lifting the other end of the see-saw, the front axle) on the front axle and can cause a deadly under-steer. Adjusted to lift to much on the rear and you get deadly over-steer as the rear end can come around on you.
The WDH also will not lift the rear end off of the ground in dips unless it is severely adjusted wrong. It is a spring bar, so it flexes as the truck and trailer move.
A WDH used with some amount of intellect and understanding of what is happening to the truck/trailer as it is adjusted is a great and magical thing. In the hands of a person who does not fully understand the interactions, it can likely be just as dangerous (deadly?) as a improperly loaded or overloaded trailer.