I think The Witcher 3 having a stronger narrative is debatable, it certainly has the more conventionally told narrative. In terms of reactivity what do we really get? How often does every storyline intersect with each other, and how isolated are they so that your decisions don't have to be accounted as widely? Don't misunderstand me, I love each Witcher game, and in terms of reactivity they're still head and shoulders over most games, but between them I have my choice for which was told more interestingly.
I didn't have your same experience in TW2, not feeling an effective story was being told in either route. Moreover the ramifications on your specific Act II had on what actions were available to you in the climax and in Act III, are part of the kind of reactivity I would like to see more of in games. And I don't think having plot points resolve without your presence is a shortcoming, it's another ramification of your actions, right?
What I will say is that Witcher 2, like Mass Effect 2, and Dragon Age 2, kicked a lot of the promise of their stories into their supposed sequels, and to a one, none of them really deliver. The actions of Witcher 2 are barely a footnote in 3. The central conflict of ME isn't really developed in 2 and the actions of 2 are usually reduced to a character being absent, or some bonus points in a minigame. I've said enough about Dragon Age
and how it fails in this regard too.
I haven't played all of Arkane's games, but if Dishonored 1 and 2 are what people mean when they talk about reactivity then I don't think they are terribly reactive, there's a hidden number that you contribute to that changes the world-state as you add to it, nothing you specifically do really is reacted to by the world, I understand that Prey
's DLC did some interesting things adding Rogue-like elements to a game loop, something they did again with their last game, but nothing about that really seems to be the same to me as what I think everyone else is interested in, having your specific actions ripple out into the game world, flipping switches that are specific to that action. I have played all the Deus Ex games, apart from the opening of Human Revolution, I don't think they did anything groundbreaking in this regard, they were fun though.
Larian has talked about their n+1 design, every quest has n
number of resolutions, +1, that +1 being what happens when a player can kill any NPC in the game. Every quest has to be resolvable if their NPCs are dead. This is technically reactivity but to me it's the least interesting type of reactivity, at least from what I remember from DOS2. You might as well have Biff the Understudy come back (with Speak with Dead we kind of do). Slightly more interesting is stealing items, so far it's pretty rewarding to see a game not break when you do this, but it still doesn't seem to have greater ramifications beyond that initial interaction. Much more interesting is when you do quests "out of order", I was really interested to see what an interaction with Minthara would be like if you meet her after getting information from Nere, and there was something there for me. To bring it back to the Witcher, a favorite narrative trick they had was delaying the ramifications of your choices, sometimes choices you didn't realize you were making, till a different act in the story. Well I see a lot of groundwork being done in the EA stage for when we make it to BG, this is the kind of reactivity that is most interesting to me because I see it as potentially having the most profound impact on my personal story in the game. It's also usually the most disappointing when it fails to follow through so who knows.
A lot of times reactivity in games seems to be mostly a euphemism for how well it deals with you killing people. Maybe it's connected to the renaissance Rogue-like games have had, and their influence on RPG design, I don't know. But it's still only the first layer of what a reactive stories can be. It's also been years since I last played either Witcher game, so maybe I'm just remembering them with rose-tinted glasses.