I last descended Black Sail pass to Ennerdale and onto Buttermere via Scarth Gap last September. I remember that we did it in torrential rain, on a walk from Eskdale to Buttermere, and whilst the path is very loose in places, it's perfectly do-able - no sheer drops. You just need to take your take time on it.
The Ennerdale side of Scarth Gap pass is pitched a lot, so it's pretty easy. You probably already know the descent down into Buttermere is also a bit loose in places.