Sweeping Lens is simply inferior to Oracle Alteration. Can we get charges for Sweeper?
I pretty much never stick with Sweeping Lens since you can sweep multiple areas for wards with one Oracle usage and enough MS. Not to mention that a stealthed opponent can easily avoid a Sweeper's zone, but an Oracle zone can chase them.
To make Sweeping Lens a bit better, how about giving it a charge system similar to Smite? Basically, you can hold up to 2 charges, but they take considerable time to acquire, and you can't sweep twice within X seconds.