Ok, so this is a broken thing then. I mean the problem is, even if he isn't in plain sight - he is still firing arrows/magical blasts at the enemy and they are just not actively looking for him at all.
Like it's totally normal for my friend to have had his head explode like a ripe melon after that blast from the shadows which lit the entire room up - "so lets not explore that situation and maybe it will go away"
Or that arrow sticking out of my friends face "must be a birthmark I never noticed."
I can bet that if the AI problem isn't solved with the last patch (the video is older), it will be eventually. Larian already know how to write the logic for that, they had it in DOS1-2. They had the AI even being nasty enough to just nuke the spot where they saw you last time with an AOE. And that light beam on the hiding spot is there for a reason.
