Jeff, I experienced the same frustration when started with WPF. As long time Autocad programmers, I believe most of us were more used to Win Forms. We usually jumps into UI to quickly build a prototype of supposed tool and show it to the business side for further discussion, and we often think through the process in OO way after quite some UI work.
IMO, it would not make too much sense to use WPF without doing it in MVVM pattern (except for super simple UI as dialog box). With MVVM, one should starts with ViewModel. Only when a meaningful ViewModel is available, the view then could be materialize by binding ViewModel data to it. Surely you can hard-code some bind-able properties of the view model with fake/test data, so that the view actually shows as expected, especially if the view has to show a collection of objects, such as ListBox, ListView, Grid,...
As for your particular UI as you showed, since it does not show collection of objects, so you still can go ahead to work on XMAL to make the UI runnable/showable. For combox, you can hard-code combox items in the XMAL for example. But you must get all the data required for this UI into ViewModel and expose them as bind-able properties correctly.
For me, if the UI if modeless window/PaletteSet, I use WPF exclusively. If it is modal UI, I only use Win Form if it is fairly simple, and no action is needed in AutoCAD when the UI is displayed.
One thing is for sure, even one is quite familar with/good at WPF/MVVM, it definitely takes more time to use WPF than to use Win Form. I'd the frustrated feel was quite similar when we VBA programmers first tried .NET API 15 years ago: suddenly you felt not being productive as you used to and so much to learn to do almost the same thing(well, we only realized that we could do more with the pains-taking learning). I am glad I can stick with WPF for most my AutoCAD UIs these days.
Not really suggestion on how to do it, Just share some thoughts/feelings.