I have a theory on that. Remember when the Dev's ask if we'd like the cap to go to 99 or 100. And most of the NA player base went off the 100 cap to gain access to some extra JA and spells. Which in turn the Dev's came back and said no because that wasn't the intent they were looking for. Well that could apply here as well. As the SP original intent might have been to give RDM an edge in survival with enhanced buff's. And by the time it got to us, we were all looking at the bigger picture of using it via accession to transfer stronger buffs to party members. Which in turn was something they didn't intend, so they decide to trash it for the one hit wonder enfeeble.
Now that's just a theory, but if you look at the history it makes sense. No one said it was a horrible idea, it just needed buffing to make it worth wild. Honestly I would have rather taken it as is than have the new one. I want enfeebling to work correctly before I have to blow a special timer just to guarantee landing it.