Ok. With so many people deriving the plot for being too predictable or impossible to follow, I think it's past time we start talking about the themes at large instead of nitpicking the story to death. Let's start with one of the most overriding motif of the game.
While going through the game you might notice that there is a lot of Buddhist influence. You can see it in the obvious with the cycle of death and rebirth, past lives and superpowers that deride from the chi. There are also subtle nuances like the way some cultures deal with past souls reincarnating in new forms (the Dalai Lama is the most famous example) and the mystical "Jade"-like substance that props up everywhere.
One of the core tenets of Buddhisms is the inability to let things go and how it keeps us from ascending to a greater existence. You can see this in the journey of the Watcher and how his past life literally drive his current journey.
This is also reflected in the companions' personal quests. For example, you get the chance to tell them to keep pursuing their objective or let it go: Edér can let go of his past or continue to follow his faith (or both), Durance can accept that he no longer is one of Magran's faithful or pursue a vendetta against her perceived betrayal and Sagani can focus on her duty to her village or the family that she left behind...
All in all, props to Josh Sawyer and his team for capturing an Eastern philosophy without making it feel too "Far East Oriental". As someone who is a bit of a "lapsed Buddhist", I found their overall commitment to the underlying themes in play a refreshing change from the sea of "Kung-fu Eastern" depictions that try to single-mindedly capture the visuals without the teachings underneath.