When I play RDM, I only start helping on raising if:
- Healer(s)' swiftcast is on cooldown and there are 2 or more players kissing the floor.
- Healer(s)' MP is running dangerously low.
- The raise is needed to prevent a wipe or serious damage to the party: i.e. only the main tank died but both healers' swift are down while boss is about to cast a tankbuster cleave or crucial mech like those in savage that requires 8 alive members (ugh.. looking at you: Ramuh's CL PTSD...).
Otherwise, no. Healers, hardcast your raise whenever you see fits. Especially if it's ASTs because they have much more leeway to res multiple times compared to other two.