I have to add another perspective. I have two accounts, both now are F2P with the occassional special event purchase, and for the last 7 months of playing consistently everyday finishing the dailys and advanced quests, which includes the requirement to use 2 CB keys. In one account I generally play NM and the other Brutal/NM. I am, I believe, a Mid game player. Also, I play several of the events as much as possible including CVC.
In this time, from CB I have only received 3 epic books and I vaguely remember receiving 1 legendary book, and I think 2 rare books, again this is since the beginning of the year, which is 7 months.
To say this is frustrating doesn't give it enough weight. However, as the subject of this specific forum suggests there are others who have legitimate complaints about the lack of books being provided for all the time and effort playing this "Gacha" game.
Since the start of covid when I began playing until now, I'm continually reading the frustrations of players, new and old, regarding the apparent lack of concern by the parent company for RSL and it is very noticable. Which begs the question, when will they listen and learn, or does it really just come down the one thing all companies want, money? FWIW
With respect to RSL, I have viewed many of their videos and found them to be typical of a company trying to keep up with growth and the demands from their "users". I must say, there really is a special art at shining people on. I still like the game, but only until becomes more a bother than like human nature, I search for something else to do because of not being heard.
You can only dangle meat in front of lion so long before it decides to eat you. ;-) Then leave.