The only reason why it feels like you did less damage in this particular one instead of it simply compensating for the squish, is that you also lost the absurd amount of BFA borrowed power. In BFA S4, you were doing 150k damage to a boss with 21M HP, now you are doing 150k DPS to a boss with 7.5M HP. So while your total damage number has stayed the same, the time to kill has gone down.
In SL S1, you were doing about 1/2 the damage you do now. So answer me this: does it take longer to kill a 21M HP target doing 150k DPS, or a 7.5M HP target doing 75k DPS?
The scaling aura in Legion was active at level 50 from what I can remember, as I know that I solo’d normal NH on a level 50 paladin in SL.