None. At. All. Both were out of place, looked confusing, and had no place in the context of the story itself.
I disagree. While AoU maybe was more egregious, especially with what they ended up showing, it served the purpose of telling Thor the truth about Vision.
Like I said though, what they actually ended up showing didn't quite convey that, as much as they spelled it out for us later via Thor himself.
However, in BvS, while yes it is definitely serving as set up for more down the road, it's purpose in BvS is very clear, and absolutely serves the story.
First of, and again, it's meant to be misinterpreted by Bruce, AND the audience, as being about Batman and Superman's conflict with each other, and the ultimate road that could lead to.
In that context, how does it do anything BUT serve the story?
Prior to that, Bruce is, while heading in that direction, not hardened in his resolve to actually destroy the Superman.
He see's the threat, he has the rage, and Alfred sees it, and states that things have changed, but Bruce still denies it.
It's the Knightmare, and the message that he was "always right about him", that push Bruce over the line, and he actually commits to "destroy him."
In other words, that's the point that Bruce goes past the point of no return. That's the point that his mind is made up about his course of action; after he sees the manifestation of everything he's feared, and he's told he absolutely was right.
He's seen that it WILL happen, that it IS an absolute certainty. Without the vision, Bruce's "If there's even a 1% change . . . we have to take it as an absolute certainty, and we have to destroy him" makes zero sense.
Without the Knightmare, this reasoning, and the entire film, is just Bruce acting out of character, and doing something Batman would never do, and it just becomes a writer and director badly misunderstanding the character.
Sure, he'd be PREPARED to do it, should Superman ever ACTUALLY become a direct threat, but Batman would NEVER push to act preemptively
THAT is the purpose the vision serves in BvS, and that is how it serves the story in this film.
ON TOP of that it also serves the SECONDARY purpose of setting up the Justice League.
Everyone criticizing it is completely ignoring all of the above, and only focusing on/obsessing over the SECONDARY purpose of the scene, acting like that was the ONLY purpose of it.