Great replacement for multiple Element Grips. Although if you used those grips for elemental spells or songs as well... You'll pretty much have to get the corresponding grip.
Any good RDM at the highest level should not need this grip. 331 skill before merits and equipments, as another person has said already, you'll rarely have issues landing anything. And in Abyssea, if you can't land something on an NM, its likely immune. Personally, I've begun swapping out Enfeebling Magic Skill gear for potency modifiers (AF3+1 hat instead of AF2) being one example. If you need this grip, you need to play something else that needs the skill. BLMs I could see them having a use for this, but then again, even BLMs shouldn't have issues landing stuff, and if a BLM is doing a RDMs job, theres issues there!