Got me thinking, comparing it(Warbreaker) to mistborn(WOA), Vin and Vivenna, are very similar in an opposite way.
Vin: A Skaa, not trusting, saved and thought how to trust by kelsier, became a noblewoman.
Vivenna: A princess, very trusting, kidnapped(saved but yeah, she's kidnapped) by Denth, became a beggar.
On the other hand, similar and yet opposite plot became to surface, hence, Vin killing, the Lord ruler, and Vivenna's sister(siri), ended up having a romantic relationship with the God King. So that's it, I think that's enough for the mistborn and warbreaker trilogy, same plot at least in an opposite way.
Comparing now, warbreaker to words of radiance is nightblood, and Szeth's sword(the last one he acquired). They both talk, and they talk about evil.
Okay, so theories, I really don't know about Hoid or Wit, I've read about them being "aware" of the other worlds, but are they really the same? Since Hoid is not really active in mistborn and in Warbreaker I can't say much, but I think that the worlds are just parallel universes. Sorry if this is posted in a wrong section, It's my 4th or something thread. Thanks for reading.
Edit: Vin and Vivenna, similar names? Plus God King and Lord ruler, yes?
Edit2: I think this should be in the theories section, sorry, if a mod read this, please feel free to move it if necessary, thanks!