I tried this last night and yes it will get FL to stop hitting/chasing you but when doing orbituary all the adds that spawn from there can still wreck you. I was in a seige and it was pretty pointless.
Yes this does work. Tried and tested. The Leviathon hovers outside of the corner and does not enter however he does still fire missiles at you, they don't do much damage but for me he did not los and reset.