I think this system is crazy. Just make it more expensive to buy stuff as opposed to random. I gree with the OP, and also believe his numbers. I am only valor level 33 and have opened at least 50 bags and have only 3 pieces, with many useless relics.
Why do people who are not at valor 50 or even 30 keep saying bs to that many bags?
You get 3 bags from the weekly Illum, 3 bags from the weekly warzone, you get 1 bag from daily warzone and one from daily Illum. You start with 5 bags when you hit 50 from saved commendations. If you play a fair amount you can buy at least 2 bags a day.
So in your first 7 day period you will get minimum 5+3+3+(4*7)= 37 bags.