Look at Bioshock, or Wolfenstein, they implement ADS shooting without gimping non-ADS shooting. Why is that bad? ADS still gives you a little bit more zoom (for wepons without scope) and increases your accuracy by reducing the sensitivity. Seems useful to me, and it doesn't gimp the other shooting method. Win-win.
I don't want them to remove ADS, I just want them to remove the accuracy penalties tied with not using ADS and moving. That approach would give you more options at any given time, and that opens up the gameplay, making it more interesting.
And I know Destiny isn't Halo, but I think removing the accuracy penalties (again, I don't want them to remove ADS) would fit the game better than the awful random vector approach they are using now, and it would greatly benefit the gameplay, especially given how many movement options you have, and the verticality of the maps.