RDM is equally screwed by a split second aoe dropping on them, although admittedly its easier to slide with the extra second they they have to move can mitigate this issue though.

A RDM dropping a cast is pretty painful though, because one dropped cast is two dropped casts. Both rdm and blm solve this problem the same way though; learning the fight, noting when mechanics happen, and preparing their plethora of tools for those occasions. That's the gameplay conceit of and challenge for casters.

Also, smn should be casting more, not the other way around making blm and rdm cast less. They're CASTERS. That's their whole gameplay theme. There are plenty of other jobs to play if cast times are your bane.