I finally completed my collection with the purchase of Greedo. Yesterday I updated the collection section in the app and noticed that in the menu to add Greedo it says somethign like "Adding this Villain pack to your collection will cause this character to show up outside his proper timeline".
Possible spoiler about some characters ... maybe ...
Then I started to have a look at other characters. There are the obvious ones like the Inquisitor, Maul and Obi-Wan whom death where shown on screen, but I also noticed the same for Ahsoka Tano. Somehow, I was under the impression she had survived the Rebels show. It does not mean that she's still alive after the battle of Yavin (the first mission of the app), but I am not aware of her death. Interestingly, Hera Syndulla does not have the text, which is fine since we see her in the ongoing Star Wars comics which time line is set between ANH and ESB.