Mine's only a 500 pound six footer, yet I don't have the issues you describe - because I use the scarifiers to render the soil into something the blades and the box can then move/grade/level. Sounds like you're trying to do everything in one pass - and quite obviously realizing it can't be done.
Of course I do the same thing.
But for most, moving the scarifiers up and down everytime you want to make the soil soft enough to move can be very time consuming so I'm sure some of the posters just try to cut level without using scarifiers first. And you (and I) are right about the boxblade not cutting good that way. That's when you get the boxblade to ride up and down the contours. From your description(s), there's no doubt that you and I operate the the boxblade in a similar fashion, I see that now. It's just that when the gage wheels were thrown into the discussion, I started thinking in terms of "grading" or "smoothing" and then trying to cut that way without ripping first. Because generally, that's what I associate with usage of the gage wheels. Know what I mean?
jshbryan's original post was about leveling. That requires use of all the techniques we've discussed here.
Sometimes you only want to take off the high points with out disturbing the low points. And then continue onward for a really smooth finish... or... just scrape a little bit more off as you continue. If you have to tilt the boxblade back to keep the scarifiers from digging in, your not going to able to take a small slice over the following section without ripping that up too.
I turned my boxblade into gear driven hydraulic scarifiers so I can rip, cut and contour all in one pass. Look carefully and you can see when I back over the ledge, that's when they are lowered. Then as I drive forward, I raise them up so they only rip the ledge and don't rip anymore after that. Then I only move the part I ripped off. If I had to tilt the boxblade back, I would deposit some dirt on the already level area ahead and I don't want to do that in this case. I set the scarifier depth travel to only 4" when the box is flat. But by shortening the top link (tilting it forward), they dig about 8" deep. You may have to replay the video to catch it?
When moving lots of dirt, I do exactly like MtnViewRanch and grab a heaping bucket full and a heaping boxblade full and deliver it to where I want.
That's a 1/2 yard bucket with a heaping yard in it and almost that much inside and in front of the boxblade. You can see the fronts squish down.