I am not really sure how you can do well sniping in Halo, but not Destiny because the aim assist is off the charts in Destiny. I recommend using ambush scope, hidden hand, snapshot, unflinching on something like a Low Grade Humility (I didn't look to see what sniper you were currently using so you might have one that's better) if you are having a difficult time sniping. Also when you say Halo, you aren't talking about Halo 4 right? If so, that doesn't count.