The problem doesn't lie with accuracy. It lies with sway.
In RO1, if you held your rifle up for more than 2 seconds, you'd start to sway all over the place.
Having less stamina meant more sway. Coming out of a sprint, immediately sighting meant you'd be all over the place. Sighting from standing position also meant a lot of sway.
Unfortunately, stamina doesn't seem to mean anything in RO2. I can be sprinting to the objective, stop, sight up from standing position, hold my breath and snipe someone 200 meters away without trouble.
There is no duration in RO2 after which your sway starts to increase (your arms getting tired). You can just zoom in and hold your breath for eternity.