I agree with you actually, but blizzard has never been perfect and will never be. The fact that people don't remember that blizzard from day one has released patches and not shared every change and think it's something that it's happening only now speaks for itself. Same people (I don't know if you) that are talking about the raid coming 1 month later forget that ICC from the best expansion evah was timegated.
- - - Updated - - -
hmmm no, mobs gain is lower than yours, I think it was something on the lines like "you are 30% better, mobs has 15% more health" (But I don't know) meaning that you will notice this 30 ilvl bump when you do world quests for example, you will kill things faster, just not 1 shot them 6 months into the expansion.
So.... 7150 residuum for a specific 415 piece.
Amount of pieces you’d have to scrap for that:
385: 205 pieces of Azerite gear
400: 63 pieces of Azerite gear
415: 20 pieces of Azerite gear
Considering gear sources, I'd say the weekly m+ chest will be your biggest source of income by far (625 for a 10 key).
Napkin math tells me that it'll take around 20-30 weeks to get enough for the 3 specific pieces you're after, call me a cynic but that sounds awfully close to the next raid tier.