Two of my headcanons about Vader:
1. People who don't know that Palpatine is a Sith Lord think that Vader is a bounty hunter hired by Tarkin. As a result, Palpatine isn't blamed for Vader's actions.
2. Vader rarely, if ever, appears in Imperial propaganda and never gives speeches on Holonet. The Tarkin novel implies that Tarkin gives the majority of the Empire's speeches.