You cannot talk to NPCs while holding control of your pet.
You cannot use Eyes of the Beast if you are in combat or start combat by pulling aggro with the pet while you're controlling it.
Eyes of the Beast Tips
Try to have teammates to guard you for when the mob is pulled.
If you are in an area where you can cast [Eagle Eye], but you cannot see your target, you can use Eyes of the Beast to position your camera (attached to your pet) to another area and cast Eagle Eye from the pet's point of view.
Greg "Ghostcrawler" Street, answering a question at BlizzCon 2013 regarding the ability's removal, said that Eyes of the Beast was actually clipped from the game code. It would be a non-trivial matter to add it back, and would come at the cost of adding some other ability to the game. He acknowledged the desire in the hunter class community to have Eyes of the Beast back, but noted that there was no great solution at the time. In reply to a question on Twitter in 2016, he more clearly stated that it was "not hard [to bring back Eyes of the Beast]," but again reminded the community that it would cost development time on something else.
The ability would eventually return to the game in patch 9.0.1, after a 10-year absence.