Funny that nobody just stop and think that not only the drop chance is probably low (and you will roll against other 9+ players), but it will also made to last more than a few levels and one xpac.
Just like other BoAs go from 1 to 80, 1 to 85, etc.
It would make the raid worth farming for longer, since a new xpac you would just throw away your gear really fast (would it still be worth farming something just for 90-95 when you get weapons from questing/dungeons at each level?).