There are some highlights in the book that suggest the world could be so much more interesting. The magic system of the plainsmen has a weakness against Iron but we don't really know what the source of the magic is (beyond a frog that can cause hallucinations). The Specks to the far west also show some interesting promise as does the magic of the mysterious "tree lady" that Nevare encounters in a frog induced hallucination. However, none of that is ever really developed during Shaman's Crossing. Instead Hobb keeps hinting at them with frustratingly similar passages over and over again.