I wasn't expecting a "characterisation shakeup" exactly - which is why I was incredibly puzzled by the direction the advertising was taking.
- emphasis on "Warrior of Darkness"
- If our powers as the "Warrior of Light" are given to us by Hydaelyn, what does it mean to become the "Warrior of Darkness"? Logically that means aligning with the opposite of our Light-power-giver, ie. Zodiark.
- Japanese sub-title "Jet-Black Villains" - if we're the Shadowbringer(s), are we also the "villain"?
- all prior examples of Darkness in the story being aspected to Ascians/Zodiark/chaos and the opposite of our heroic efforts
- trailer scene with taunting gremlin implying we were all alone in a desolate Light-soaked wasteland (didn't happen)
- pre-existing implications from the Warriors of Darkness arc that Ardbert's group caused the Calamity by being too good at being Warriors of Light and defeating the Ascians on their world, triggering the Flood.
- combining those two points, the implication that we triggered a similar flood because we defeated Zenos/Elidibus.
- a following conclusion (now known to be based on incomplete information) that Hydaelyn's command for us to fight the Darkness and spread Light might be anything from 'a bad idea' to deliberately evil, causing us to turn against Her.
- the ominous command to "become what you must", ie. something you maybe don't want to do, but have to. I think this was from the first trailer, long before we knew the identity of the mysterious voice and had reason to trust him.
- Dark Knight, the story that puts a darker-and-edgier spin on your characterisation, as the "poster job" for the expansion.
I didn't want it to happen - if you browse back through the Lore forum at that point you'll probably find a lot of me saying "but we can't go that direction! It doesn't work with the rest of the story!" - but it sure looked like it was the direction they were going, and I was expecting to be dragged unwillingly down that path and hoping there'd be a good explanation at the end.
As it turns out, the explanation seems to be "we wanted the trailer to look impressive".
(See also: the "just there to send us into theory meltdown" scene of Y'shtola being addressed as Master Matoya. The actual explanation for that felt so weak that I would not be surprised if they invented the entire plot point just for trailer shock value.)