I ran Shadow Step on every boss. I can't think of a situation in SoO where BoS would be a gain over ShS. I could maybe see Norushen, but the comparison basically looks like this:
- Kill big add
- BoS to every little add, do some damage and kill it/let DoTs kill it
- Use Sprint at some point to save energy or go faster if glyphed
- Rupt big add
- Pull big add to #1 little add and kill it/let DoTs kill it
- ShS to #2 little add and kill it/let DoTs kill it
- Re-Rupt/finish off big add
- Sprint to #3 little add, do some damage and kill it/let DoTs kill it
- Keep Sprinting to #4 little add and kill it and ShS back to any others if needed
ShS is more complicated, but probably faster. BoS is probably better if you don't want to bother. I just like ShS though.
It might be a good crutch on H Blackfuse, but definitely not necessary once you get the hang of the rotating beams on the Conveyor Belt.
EDIT: Oh, BoS is probably a good idea on Thok, as the post below says. I assume this is to allow uptime during the kite phase? I didn't think about this because he ate you if you got anywhere near him on PTR and did not try hitting him on live. I'll see how DPSing him during kite phase goes this week.