I don't know how many safe scenarios would be recommendable for empty Shine TA Bair......maybe if someone is in front of your shield and you don't want to grab them......but to edge guard in a Sheik/Marth situation they would just fair/nair you before you get too close....
Mostly i was talking about when a character is in hitstun above and in front of you, such as when you dair them at high percents. Its a great combo finisher.
However, you'd be surprised how often it work on many chars recvoery.
Firstly, you can use it to edgeguard any recovery which is either directly horizontal (fox's illusion) or predictably vertical (falcon/Ganons B-up)
With marth, if you can guess when he's going to side-B, you can drop from the stage, empty shine TA bair him because his side-B has massive lag.
these are just a few examples, and there are always other options to edgeguarding.
What im saying in, Shine TA bair is great in a lot of ways, but its not the best thing ever, use it if you want, or dont, its not
essential, but its falco's best horizontal finisher when you're moving forward. You could also just do regular Bairs that hit such that your opponent is sent forward, but in my experience those are way easier to survival DI because of the nature of the hitbox