I think with the PG/VG comparison, you're equating viscosity with richness. This might hold truth for edible beverages and food stuffs, but holds little ground in the world inhaling vapor

Though I don't really know the exact chemical rationale behind this, as you put, paradoxical happening, I understand it by a basic concept of VG = thicker, therefore the flavoring is competing with the glycerin more so than PG = thinner, the flavoring has less to compete with.
This is, of course, a very lay way of looking at it

But everyone understands, and comprehends things differently. Oh, how fascinating it is, how human beings think, and the individuality of it all. However, that is a conversation saved for drunken ramblings around a bonfire. Back to the topic at hand.
The magic number will always be different. And this is because of multiple elements. The flavoring used, individual tastes, pg/vg ratio, are just some of the mechanisms that add up to the machine that is your goal. You could always take one of those successful blends you've mixed, and make a small bottle with an increased amount of flavoring to test. Personally, I have never seen a recipe in the DIY section here with someone using 50% flavoring. Heck, I might even try it myself, for shins and grins