Hey Tony,
While I hear what you are saying (about your last photo), I think you are a bit too critical. My first feeling is that the shot is quite interesting. Yes, there are differences in light, but 99% of people who look at the image would not notice it. Not even slightly.
I also think that what you said about letting the light tell you where to put people is very important. It is the key element. Work with the light you have. Follow it. However, in outdoor situations, I find that I always come back to the flash (at least for portrait work..I generally do not flash wildlife).
James