Wrapped up chapter six and honestly surprised people had such a hard time with it. Use your gear, nerds. Not having BB presents a challenge in not being able to see BTs at all, but hematic grenades are an easy solution to a very simple problem. Soon as you get spotted dropping a hematic grenade right on top of the BT stuns it leaving it open for a very easy cut. The huge blood cloud ensures you'll hit, and if you don't the BT is inevitably going to walk into it while coming after you. I only got stuck in tar twice during the chapter and wriggled out of it both times, dropping a hematic grenade right on top of them the moment I could. Spotted by BTs a couple more times, which again were easily dealt with using the hematic grenade.
I'm playing on hard too, so no real cheesing. Sometimes I think people are presented with unusual problems and just don't stop to think how they might be able to adapt. By the time this chapter drops you've got a pretty enormous helping of combat gear to fabricate, and a good chunk of it explicitly deals with BTs.