Pale Tree Vision PoI
You absolutely can get to it later, it’s the entrance to the Arah dungeon which you’ll need to do for the penultimate PS step. The areas you travel in the vision are actual areas in Orr.
However, in the vision you have far fewer monsters to fight on the way to said areas than you will be dealing with at level.
edit: Also a note: I don’t think you keep the pois from the vision. I certainly have had to re-explore them once traveling in Orr. So they’re just a nice little xp boost while in the vision.
You don’t need to get the PoI’s in the personal story instances to get map completion, everything can be gained out in the world. So your are not locked out in any way
One exception — I’m not sure you can get the poi in Fort Trinity where Trahearne holds meetings unless you go in via your PS or someone else’s. Not without some sort of wall running glitchy action, anyway. Or did they change that?