I think you are absolutely correct in emphasizing navigation skills, but I would order the priorities a little differently. A good map (or possibly very good knowledge of the terrain) is first priority. A compass also ranks high, although very often it is not necessary - there are many ways of determining direction. A GPS is really useful, but not what I would call "essential".

PLB's are debatable. Actually, most of the time a cell phone will actually be more useful and will afford better communication in event of an emergency- as long as one has coverage. With a group, a PLB is less critical, but the solo hiker, or an inexperienced group, would be well advised to pack one.

The Essentials, whether ten or more, will vary with the circumstances and the surrounding environment. You need a lot more water in the Arizona desert than you do hiking in the Sierras. Hiking in really rough, broken country, I have long packed at least a minimal climbing rope and a very small amount of related climbing gear, stuff that I jettison in milder terrain.