I'm late to the party here, but I use a fret rocker a lot and find it to be very useful within its limitations.
Mine is older now, and I think I did have to lap one edge to perfect it, but it was pretty good out of the box.
You do have to be extremely careful that the tool is properly aligned. I level my frets conically, following the paths of the strings. So the fret rocker has to be located at the string and follow its path too.
If you level all your frets parallel to the center line, then the rocker needs to be parallel to the centerline. A very small misalignment will make it seem like you're on a high fret.
Mike didn't say if he checked that the suspect frets were still seated properly. It's happened to me a couple of times that a fret has popped up after the customer took the guitar.
As for the neck jig... I don't like the way it simulates string tension. Almost all of the force of the strings is compressing the fretboard. I get better results when I level using actual string tension and holding the guitar carefully in the vice in a way that doesn't flex the neck. I had one and stopped using it.
I've never thought about slanting the fret rocker along with the strings, but it's a good practice and very easy to do, so I will do that. The difference is maybe in the thousands of a mm though :-)
I doubt that strings at tension will compress the fretboard much, the wood is very stiff in the end grain direction. The bending effect on the neck from the tension is way bigger. I really like the neck jig, it works fine for me, and it is also a perfect working table to secure the guitar when sanding the fretboard, mounting inlays, repairing splinters and cracks in the fretboard and crowning frets.
Hi, after a few years of using the wooden early style of this fretting jig the new model was an interesting proposition, the cost was not so attractive at around $1000,00 landed in Australia. So I made my own version and it works well. For my small workshop volume, I could not justify the cost. It normally has two dial gauges and of course, takes acoustics too.