This isn't for me, but a friend of mine on my server that plays. He has been tallying up how many times he has defeated Ifrit HM and the weapon for the Scholar refuses to drop. He has tallied 61 victories over Ifrit and not one drop. I, too, have personally tallied around 20 Ifrit fights and have never seen the Codex drop either.

I don't know if this is how it is supposed to be or if the coding for the Ifrit HM fight in Faerie server needs to be worked on so that the Codex actually drops at an equal rate as the other weapons.