I get what you are saying. He is not in the area because he knows Astarion is there (it is blind luck). He is there to ask the hag for help finding Astarion.
My issue is that the hags house is 200 miles east of Baldurs Gate. According to the guard in the grove, Baldurs Gate is a 10 day walk to the west and that is if the roads are clear. Which they are not. So why is a hunter 200 miles east of baldurs gate hunting Astarion who was just abducted maybe 2 hours ago? No way this hunter was hired and managed to travel there that fast. His presence feels extemely forced and I am pretty sure he was just thrown in to open up some conversations about "Gurs" and Astarion's past.
They can fix it however they want. Whether he simply doesn't show up near the hags house for say... 5 days or shows up at camp or whether they thrown in some lines about how the hunt began a week ago. Of coarse I would love more companion options, but at a minimum I think they need to fix this hole in the fabric of the story.