I also replayed demo this week except Siegecrafter HC and Garosh HC where Iam needed for AOE and burst, Iam 578, I dont have HC Black Blood, not even normal so I went with hcwf multistrike, Iam sure Black Blood would make a difference.
I think demo needs a buff in single target department, most probably wont happen anymore they just did a hotfiix to several classes that needed it.
Destro and aff are too good, and Blizzard doesn't seem to think on specs especially on pure DPS classes