Using triplecast raise would cost BLM nearly 2000 potency in opportunity costs, if not more considering all future fire 4s and despairs they'd miss doing it. That's far and away beyond what dualcast raise (x3) costs RDM. Also using an instant to raise someone means BLM has one less mobility tool for when it counts, which is also something RDM doesn't necessarily need to consider, or at least not to the level of BLM.