Well its not only that, but Elemental Seal effects anything thrown at the mosnter, including your enfeebles and other misc spells. Bind works well vs Aquans too. Fast Cast at that lvl..i forget the exact percentage but its nothing uber high or noticible on Cure spells. Maybe a bit more with Regen.

You get Sleep if you are lvl 40 WHM subbing BLM, i forget the RDM's lvl, however Sleep is based on your Enfeebling Magic, hence if you do lvl it up decently, it should land just fine, and if it doesnt theres Elemental Seal...dont forget Sleepga for /BLM later too.