Players put down a lot more wards in high elo than they do in low elo. So if you go with Oracle Lens in low elo, you're gonna find a lot fewer wards, which means your vision score is going to be a lot lower.
I've been picking Oracle Lens as a jungler because I like to sweep the dragon / baron pit, especially if we're trying to sneak an objective, to ensure that they enemy doesn't see what we are doing. But since I'm in silver elo, the majority of my sweeps actually find not a single enemy ward, which is fine. It's just as helpful to confirm that the enemy did NOT see our attempt at the objective, so it's not a "bad thing" that my sweep didn't find any enemy ward.
But my vision score's have been REALLY BAD, and it's causing my grades to suffer. After thinking about it a while, I realize that it's partly because I'm in low elo, and Oracle Lens probably gives half as much vision score in low elo as it would in high elo where the enemy team would be placing a lot more wards down.
Perhaps if Riot could modify the math, so that if the enemy team has fewer wards on the map, and I actually find one, it would give me more credit. Simply because I wrecked the TINY LITTLE BIT of vision that the enemy team actually had, lol.
But honestly, I've asked for this before so I'll ask again, I think Oracle Lens should give some vision score if you scan an objective pit, even if you don't find a ward. Because proving that there's no enemy ward IS HELPFUL to your team, and it seems wrong that it gives no vision score for that.