I've actually noticed that, if you warp into the bonfire right before the Aarena and stay out of sight, thebyss Watchersgoing up the road will attempt to slay everything in their path. Key word being 'attempt'. Chances are at least one of them will die to regular enemies, and the other will be weakened enough so a few fireballs will kill him easily.Darkwraiths
Still kinda on the fence with the boss weapon choice, btw.
There are a couple optional stealth set pieces in DS3 that I've encountered and they've both been pretty interesting.