Random thought: Every time people mentioned PV was overpowered, 343 (mostly Frank and David here) have said that it's not overpowered at all and that mostly bad players would use it. If this is the case then why did it get nerfed?
The situations where PV is under powered may be scenarios where the game is moving fairly quickly. Slower games (i.e infested with campers) benefit much more from PV, not only that, a team with good map control should be able to overpower their PV using adversaries. While a still player can't be seen on radar, PV can still see them. The largest problem with PV seems to be the ability for the user to completely avoid and gauge encounters.