I agree that Anbu is drastically underutilized and underrated. I've said before (not here) that Anbu should have been written as a stealth unit (like Splinter Cell) that use means of hiding their presence and assassinating their targets without them knowing. Instead, Kishi wrote them as weaklings who run out blindly and use jutsu like any other ninjas (idiot move). Honestly, if Anbu had've been written like I said (stealth unit), they would have the capability to take Akatsuki-ranked ninjas with ease.