Viewpoint Assassination: The Firebrand
The Firebrand assassination begins in The Minster located in the city of Jorvik. How you enter The Minster doesn't really matter. I came in through an opening in the tower but you could also enter through a door on the ground floor. The cutscene doesn't begin until Eivor reaches the room off the second floor catwalk.
This mission has a lot in common with Jubair al Hakim in the original Assassin's Creed. Both are in the process of burning texts, both shove a guy who objects into the fire, and both spread out into the city among a number of "decoy" body doubles. Even the dialogue is similar:
Jubair: These bits of paper are covered in lies. They poison your minds, and so long as they exist, you cannot hope to see the world the way it truly is.
Firebrand: The vellum that burn before you are covered in lies. So long as they exist, you cannot hope to see the world the way it truly is.
I had just started using a predator bow (Petra's Arc) and decided to test its range. To my surprise, it was easily capable of a headshot from the top of the viewpoint on The Minster. The scope was able to identify the target by her real name (decoys say "Firebrand?") and aim with adequate accuracy. No need for that Ability to steer arrows in flight.
Once again I had to descend and run hundreds of meters just to "confirm kill". In the early games it was more dramatic to enter the Memory Corridor from wherever you stood.
Every time I've played this mission the real Firebrand has been in the same location (the marker farthest away, just like Jubair). So I don't think her location is randomized. She's pretty easy to kill. There's a beam protruding from the roof over her head for an obvious air assassination. If you aggravate her she fires arrows at Eivor while backing away.
The easiest assassination is a blitz: kill The Firebrand before she exits The Minster. She and the decoys pass right below Eivor on their way out the back door. If you're fast enough, hop up on the rail and do an air assassination. Follow up with a chain assassination in case the first one was a decoy. Even if you're not fast enough, drop from the rail and follow the group, assassinating from behind. I think the real Firebrand is the one in the middle.