Der_Orso
A good effort it is not all correct.
The situation described in She Who Knows is definitely not 3 years ago. It describes the timeline as a long, long time ago. Don't know about you, but 3 years isn't exactly a long time.
Also we most definitely do have evidence of both the Crones amd the Whispering Hillock having influence in more of Velen than just the bog.
For one, there is Keira's dialogue which says she had dreams that told her to wander into the bog (obviously the doing of the Whispering Hillock).
Lastly, there is a whole lot of villager dialogue and notice board messages all around Velen about venturing into the bog, the ladies of the wood etc.