Despite all the work Grinding Gear Games put into it, the team has decided to not keep the Bestiary league as part of Path of Exile‘s core game. Among reasons for dropping the bestiary are the facts that it would require a lot of resources to maintain and would need attention when any new features are added to the game.
Another issue is that the Bestiary strays from the makeup of the core game, resulting in it needing additional tutorial elements the devs don’t want to throw in with the already existing catalog. And, if that weren’t enough, they also feel that the crafting system would need constant work that isn’t worth it due to leveling item crafting already being taken care of in more streamlined ways.
Despite Bestiary being removed from the core game, GGG does state that some parts of it may return in future content. The entire thing may also be brought back for temporary events. In addition, Orbs and imprints will still be around. They just won’t have any function.
Judging from the announcement thread on the game’s forums, it seems that players are generally happy with this decision. Although, a few people did express disappointment.