I have seen many hundreds of posts on different forums complaining about how many Brayflox HM runs they have to do to go from Atma to Animus. Too many myth!
I feel that the idea from the developers side was to make a big challenge that would take a long time. But they did not expect players to try and do this challenge in less than 2 weeks. Certainly not in 1 week! But many players have and those players that I know of that have animus have now shown clear signs of burning out. They do not feel that this game is fun anymore since they have bad memories from spamming myth runs.
The only way I see to make this challenge in a way that will not burn out players is to set a time limit. example: you can only complete one book per week, same reset as the raids.