Hot take: Chapter 4 would've been scarier without Doey
To me, the chapter could've focussed a lot more on the Doctor and how dark the prison was if Doey wasn't there. He's a cool character, admittedly, but I feel like he makes you feel a lot safer, as you have an indestructible companion to aid you.
They built up Harley for months, only for him to be tossed aside by some random character we literally met a week before the chapter dropped. Don't get me wrong, I love Doey as a character, and he has a really dark concept for a character, but he just isn't scary to me. Harley should've been present throughout the chapter in the background, on monitors or in cameras. He will alert Yarnaby to your location so you're being hunted throughout. Once he eventually gets killed off his death actually feels meaningful and satisfying.
The Doctor was originally going to tower over the player, which would've been much more intimidating.