OTT mystical superpowers are best kept imo to one short drugged up sequence if you must have them at all. I like Primal most when it is trying to be true to a gritty hands on period. The Stone Woman is simply a clever representation of Mother Nature in a shape known to have been used - if not on such a grand scale - as the huge statue in the sequence.
Would be fun to have random vision missions from the shaman after killing the bosses and completing the main story, something similar to the story line ones but different, more like a dream world to relive old memories. Don't know if the game has the capacity to generate a mission that is somehow different each time it is done however. Maybe have the shaman make up some concoction from different plants and take a drink... Feels like a lot of work was put into the vision missions even though they are fairly short, would be nice to bring some of that back later. Cave men had dreams too, just seems strange when you rest at a camp site and stare at the sky.
I think that Primal is one game that could have a ton of DLC's and still just be scratching the surface of how big it could be made.