I like it!!... but-
Why are they pacifist? It seems very unsusual that a class built upon harnessing the souls of their enemies is squeamish about killing. It also seems that they will quickly fall behind in combat ability as they level compared to other classes- Although Soul Barrage is very nice at the end. Maybe making the soul lance a more powerful scaling attack- similar but not identical to the Warlock's Eldritch Blast.
Great idea though I like the concepts just confused on some of the fluff.