Well, it would have to be something like the passive of Duskblade - a one and done deal that has enough time to block and let you clear one ward, maybe 2, and that's it.
Yeah I could see that being balanced.
Just spitballing here but what if it reduced the cooldown of totem/sweeper by something like 50% and increased the duration of any wards/sweeps by 15%? This would mean at level 1, over the course of the 2 minute buff, you would regenerate 1 full warding totem charge (instead of half a charge), and a ward placed during the buff would last 104 seconds (instead of 90.) If you have sweeper instead, you will regenerate 2.6 sweeps (instead of 1.3), with each sweep lasting 11.5 seconds (instead of 10). If you had farsight alteration, you would regenerate 1.2 charges (instead of 0.6), and it would reveal an area for 5.75 seconds (instead of 5).
Maybe those numbers are a bit high but that seems like another angle a vision buff could take.