This is the new pet AI ‘improvement’ to keep your pet alive longer. Your pet no longer draws agro from a monster that’s not agrod on the player (to avoid the pet pulling distant monster). Your pet also now attempts to take a position behind the monster and stay alive longer. This basically means ‘you’ are now the primary target and not your pet.
As a ranger risen are incredibly frustrating, I hate this whole switch of aggro thing. screw that