It is best to set the vision range to the range of the unit's weapon. Also, the ShroudClearingRange should be the same or slightly bigger than the vision range. If it has an anti-air and anti-ground weapon (like patriot batteries or gattling tanks) then the vision range should match the anti-ground weapon and the shroud clearing range should be a bit bigger than the anti-air weapon. Don't forget the AutoAcquireEnemiesWhenIdle line in the AIUpdateInterface module if you want it to automatically target enemies when idle.