I see it like this:the planets give the frame, the outline, and the asteroids give some details, but are usually dependent on the frame.
But within that frame their accurateness can sometimes be almost creepy.
Say you share synastrically a Moon-Pluto conjunction with someone which squares Mars in his chart and Saturn in your chart.
That would be the frame, and it already gives you a clear perception of the kind of vibe that would be between you.
IN such a chart I wouldn`t really like to find exact Nessus-Dejanira or Nessus-Venus or Dejanira-Mars aspects. Could definitely tilt that obsessive, though restrictive passionate interplay into an abusive direction.
In a chart where the major players get along easily, like say a lot of action between Moon and Venus, Sun and Jupiter for example, such a Nessus-Dejanira or Nessus-Venus aspect could be a hint towards a certain posessiveness and also enhance any kind of sexual attraction that might be between people, but most probably it will not have the disastrous effects it *could* have in the first example.