RDM May Need Separate Gear Line from Other Casters - Spell Speed

[StouterTaru]

Question from the not having played RDM yet. Right now, IIRC, RDM is highest DPS caster.

So, if SS is the dominant stat on the shared gear, and SS is more beneficial BLM and SMN, would the said stat be a balancer between RDM, BLM and SMN?

Or it means spell speed is more powerful for RDM, and that's why they are the top dps caster.