I would not use a new volume, which is more work, I would go about disabling affect AI on all the actors with the bulk edit tool. I don't know how much it will improve the scene, but it would reduce some work load, as I am sure the nav mesh has to update at runtime due to building and destruction of the world.
instead of turning off 'can affect navigation' 'nav mesh' on 10k actors, could i just put a huge AI blocking volume over the world?
I would not use a new volume, which is more work, I would go about disabling affect AI on all the actors with the bulk edit tool.
I don't know how much it will improve the scene, but it would reduce some work load, as I am sure the nav mesh has to update at runtime due to building and destruction of the world.