I know there was an alleged “fix” for this posted after launch, but my opinion is legacy scaling for Legion content is still broken especially with regards to Boss-flagged enemies i.e. raid bosses.
I just attempted to solo Worldbreaker in Mythic Antorus as a level 60 warrior in ilvl 171 gear with 180+ weapons. Already on the trash before-hand, I could tell that I was still dealing far less damage to these mobs than I was last week at level 50 in my weekly pug run. Even Ancient Aftershock still wasn’t hitting nearly as hard as I would expect on mobs now 2 expansions old especially in comparison to how hard it hits some current dungeon trash packs. The main “scaling” thing I noticed was that my damage taken against the level 47 trash was almost nil.
Fast-forward to the boss itself and most of the above went out the window. I was still dealing about half of my level 50 DPS as a level 60 and the damage taken scaling I enjoyed on the trash seemingly vanished. It was only just in effect enough for me to be able to out-last the boss but it took 4.5 minutes to do it.
This content is two expansions old. Most of Mythic Hellfire Citadel aside from Archimonde was quite trivial at BFA launch in half-M0/half-Heroic dungeon gear. Please adjust the scaling, whatever it takes.