Celerity is the casting and recast time Stratagem, if that's what you meant. I don't even know if they stack to be honest (not an issue for me), but if it does then it's not very rewarding for RDM. For WHM it's useful in certain cases (as I mentioned, Raise, Reraise, Teleports, etc.).
So does /SCH, and also Reraise, unlike /RDM.
It's not simpler at all. SCH has many JAs, but none of them are even needed to make it more efficient for WHM than /RDM is. Just hit Light Arts once and enjoy all the benefits for two hours. You can time it perfectly with Afflatus Solace that way. If you don't have a Refresher you may also want to use Sublimation, but it's just hitting one JA (or one macro), both for activation and for usage, which is easier to handle than casting Refresh (no magic aggro, no casting time, no interruptions) and doesn't cost you MP. Also, since you were talking about inside Abyssea, it's not even needed there. It's hardly even needed outside on pretty much all content except Voidwatch. So you just need to hit one JA every two hours, whereas on RDM you have to deal with Refresh and Convert all the time.
Depends how you play. For pure damage output, /SCH will win too. BLM gets no MAB from /RDM, the casting time is a bit lower, but the recast time is larger. MP conservation with /SCH is better in general, Dark Arts will reduce MP cost in general by 10%, Parsimony will reduce MP cost by half, and you can use it every two minutes, Aspir can be AoE'd (and won't wake sleeping mobs, making full MP recovery possible in some cases), and Sublimation will provide about as much MP as Refresh.
However, /RDM has an edge for soloing in that it has Gravity, Phalanx (nice for hoarding mobs to AoE them, think for trials), as well as Cure IV and Haste now at sub level 48. /SCH only gets Reraise as a utility spell over /RDM.