I go to the bonfire at the top and headed back down a little to try invading, so I spawn on top of a beam where the huge blades swing from. If you drop from that to the narrow bridge under and walk towards the platform with 2 trap switches, you can head up half the stairs, and see the entire area with swinging blades, including the first and second bridges. Remember the first bridges with swing blades and serpent men? Yeah, those. All the way from the top. If you find a good spot to stand on the stairs, you can snipe all the way down there. Managed to knock a couple of white phantoms off those cuz they're so darn shiny.
And then they go to the canon ball area, which is out of reach. I waited for them to come back to the bridges, and that's where its the perfect distance to snipe. One kid even told me to go away after I knocked both his phantoms off. (Helped him get thru Sens afterwards and even showed him where to find the cage key and Logan. Good kid)
If they survive that one, the very last bridge, the one that leads to you and the switches? That's the fun part. I stayed right at the end of the bridge, perfect straight line to the bridge and the host and phantoms. First they need to deal with the serpent man throwing lighting on their left. Then there's me and my super staggering arrows. They'll have a hard time getting thru those swinging blades to start with, now there's me and my arrows that will stun them still, right in the middle of the swinging blades. The only way to get to me, as far as I know, is by having a phantom stand and block in front of you, while you shoot sorcery/arrows at me. So far no one has done that. And then I still have 21 casts of force I suppose if you're good at roll timing, you can get past me. No one got to try though, cuz some phantoms just stand right behind the hosts, so when they get hit, instead of staggering backwards, they slip off sideways.
So glad I got to 20 strength