Your right, ideally it's best to adjust a WDH under loaded TV/TT conditions.
Note that the objective of a WDH is to return the weight that was removed from the TV's front suspension back when the spring bars engaged via proper WDH adjustment. We use fender heights as an acceptable means to get the proper weight distribution in the ball park..., a CAT scale is the only way to confirm. Your correct that moving the ball mount up/down on the draw bar is the proper way to adjust TT levelness.
Today's TV suspensions are a lot different than years ago, so it's normal to Esperance a 1" to 2" drop at a TV's rear suspension when the WDH is correctly adjusted meeting the TV's front suspension requirements (return to it's unhitched height). If one attempts to raise the TV's rear suspension to much via the WDH adjustment it may result in forcing the TV's front suspension below
it's unhitched height..... not good. This could result in poor steering and front suspension performance.
If you can post a close up pic of your WDH hitched up, this may help us with your WDH adjustment. Also, review the top portion of the following link on adjusting a WDH, it may provide some insight: http://www.rv.net/forum/index.cfm/fu...d/17730894.cfm
When adjusting your WDH ball mount tilt and number of chain links under tension, ideally you want the round spring bars to be parallel to the TT frame, or a "slight" downward angle is ok.
Hope this helps, but feel free to post any additional question you may have.
ps: Your right, unfortunate most RV dealers are clueless to adjusting a WDH correctly.