Dave makes some interesting observations there and they illustrate one of the major problems facing the newcomer to Astrology, or at least its Western counterpart.
Any approach to Astrology will change over time, grow, develop and evolve. However in the West this process has been complicated by two major fractures. The first of these came with the fall of the Roman Empire till it's reintroduction in the Eleventh and Twelfth Centuries and then after the end of the Sixteenth Century till it's revival at the beginning of the Twentieth Century. Although during both interludes there were still practitioners, it lost its academic status and tradition. This meant that in both resumptions, there was a major rediscovery, or indeed development outside the tradition. The first resumption was dominated by the revisions of Arabian and Persian ideas, the second by Theosophist and later Jungian views, though there were and are many other offshoots.
This leavers Western Astrology much more diverse (and some would say richer as a result) than it's cousin. Jyotish (or Vedic) Astrology which has an unbroken tradition of nearly 2000 years. There are different takes on almost everything you can think of, and of course it's difficult, not to say impossible, to predict what Astrology would have been like if those interludes had not happened because it would have developed and changed in a number of ways.
Originally aspects were nothing to do with division of a circle, or harmonics but to the possible ways in which a perfect figure could be inscribed in a circle. Threes (Cardinal, Fixed and Mutable signs) and fours (Fire, Earth, Air and Water) create the Square and the Trine or Trigon. The opposition gives a single line and the Hexagon the Sextile, all other of today's minor aspects fail to yield a figure that fits perfectly into the Zodiacal Wheel, without significant distortion. (see
http://www.skyscript.co.uk/aspects.html)
Also it's possible that aspects originally were by sign, not by degree. However certainly by middle to late Hellenistic times the degree was the main criterion used, rather than sign (though out of sign aspects were not recognised). The inconjuncts - the semi-sextile and quincunx were not seen as aspects, the semi-sextile being seen as too obtuse to be useful and the quincunx to give no relationship (though as I pointed out earlier this doesn't mean that nothing is going on).
It's quite possible that the minor aspects would have been developed anyway or that harmonics would have come into use (as harmony is an essentially Greek concept) but whether the meanings would have been the same as modern ones, is impossible to say.
Thus we are left with far more variety and possibly far less astrological basis than we might have had but there's nothing we can do to change that. It's a fact that we have to live with and the new student has to cope with. Even those of us who seek to build on a traditional base, can't say for sure what the tradition is, because so much has either been lost, or is subject to difficulties in interpretation - that is to say a clear understanding of how Astrology was practiced.
Personally I'd say that an Astrologer needs a clear system and techniques that fit that system, rather than dipping into a variety of possibly incompatible systems and techniques. Until you are able to do that the practice of Astrology will always be confusing. Start with a basic or introductory text, keep to major aspects before you try minors, harmonics or midpoints (or Greek Lots/Arabian Parts) and the minimum number of bodies which you feel comfortable with (this is usually the 7 classical plus the 3 'modern' planets) and only add as you feel real need to explore beyond your thorough understanding of the basics.