I agree that Vincent probably gaslit Xavier where his visions are concerned and made him think whatever he was seeing wasn't real and didn't believe they were true so he wouldn't say anything which makes me think that it's possible he's always had really dark dreams/visions which were played off as regular nightmares which just got worse the more trauma and pain he went through and the stronger his emotional state, especially if it was bad got which all collectively started impacting his mental health and would've made his visions even worse.
It's all such a horrible situation for him and the more you look at it the more you realize how much he suffered throughout the whole season.
I hadn't considered that the outcast community doesn't believe or listen where visions are concerned though. It would make sense and would explain why he kept things to himself even if he suspected they were real because there wasn't anyone on his side or who he thought would even believe him.
Yeah, Xavier suffered a lot in this season, but he almost always kept quiet about it. The camera really only follows Wednesday's journey, so it's so easy to overlook.
There were so many times when he was just doing his own thing, like looking at a blank wall, or trying to go to his private art studio, and Wednesday just shows up to distract him from dealing with his own shit.
Again, a some of his bad times just off the top of my head:
When he was young: his godmother dies, and he almost gets burned alive
A year ago: his mural gets destroyed and he gets assaulted
At the beginning of the year: He gets manipulated by Bianca's siren song so bad he has to break up with her
A few weeks before Wednesday arrives: he starts getting horribly gruesome nightmares that he can't help but paint
He gets assaulted by his roommate
Wednesday blows him off multiple times
Ajax doesn't switch outreach day assignments
He has to work at the Weathervane with Tyler, his attacker
He finds out that his roommate did actually die
Wednesday doesn't believe him when he says he's not the hyde
His family doesn't come to parents' day
He gets arrested and thrown in jail
His father doesn't come to see him when he's in jail
The sheriff leaves him locked in a car when there's a monster on the loose
And he was already a tortured artist by Enid's standards before Wednesday arrived smh