I never saw Soren as an absolute dick, I saw him as a pragmatist. Aside from a few isolated occasions where he lets his emotions get the better of him, (a la chapter 8,) Soren demonstrates that he makes his decisions based purely on the well-being of the Greil Mercenaries, not committing to anything unless the company can benefit from it.
Soren's pragmatism is most heavily demonstrated in the beginning of Chapter 5 in Path of Radiance--while Shinon wants to side with Daein purely so he doesn't have to step foot in Gallia, Soren does so because Daein was winning, and because he believes that fighting them is foolish.
What I'm getting at is that people like Soren because he's an amoral character surrounded by a morally-driven party, and that dynamic is fun to watch.