I remember many years ago trying to cover buff yellow primer spots with some dupont chromabase, the base in the three stage laser red color, it was unbelievable how long it took to get coverage. I don't think choosing buff colored primer for a base is a good choice most of the time. I looked up the prowler orange on duponts european site, and although it doesn't show chromabase, the lines it shows gives a value shade #4 also, which I would believe would be a medium grey, somewhere in the middle between white and black. Looking at the formulas for the dupont mixing codes on the european site (not registered so I can't look at chromabase ect) it shows mainly gold, and transparent red, which would make sense why it wouldn't cover well. In fact, on many lines on the european site it is marked as a poor hider.
When you first get your paint, stir it. and then take a look at the stick and its edges. If you can easily see through on the edges of the paint stick, and it looks very transparent, you can pretty much be assured that its not going to cover real well. A trick used in bodyshops besides sealing with the right color sealer, often if you have a color that is transparent is to use a different basecoat that is close as your ground coats. Maybe an orange/gold color? Then even though you may not truely have full coverage and may see a little of your ground color through, it will look even, kinda like a candy. Its seems like a lot of colors cover poorly nowadays. After running into a few in a row that took 4 coats or more to get coverage, I asked my paint jobber what the heck was up. I said I didn't remember too many colors that didn't cover in a couple coats years ago. He gave me the excuse somewhat to the effect of with the greater number of high impact more brilliant colors yada yada, that are popular today, there are lot more toners used in the mixing formulas. Okay whatever, I think they are just putting in a greater amount of binder and less tint or something. There has always been transparent red, yellow, ect on the banks.