Range vision is not the most attractive attribute for a technology. In the future we will certainly be able to find another way to make it more attractive to players.
For now I think 250 metal for sibylline books and 200 food / 200 metal for exploration too expensive for that purpose, how to discuss, so the patch reduces the gain to 20% and the cost to 100 metal for sibylline and 100 food / 100 metal for explorationit is best to remove these two technologies.