well the only true person to see Dexter cut off limbs in the series was Lumen, oh and Doakes but from behind the plastic sheeting. He never let miguel see that part of him.
Like he says "i'm not ready to share that part of the ritual with him yet." BUT honestly to up the anty a bit, i think they should show it once before its over, let us see the whole process, and it won't make us dislike him, we already know its happening. At this point with Deb now knowing, i saw anything should go with the show as long as the writers pull their head out of their asses, and I pray they end it right. I really don't want our favorite killer dead in the end unless he ends up having to give his life to save Deb and Harrison. but still i would be upset that he dies in the end.