The easiest way to fix the issue is likely in encounter design. If there are more instances of raidwide moderate damage instead of big bursts every minute, SS would inherently lose value without needing to nerf it.
Otherwise, what’s the proposed solution? Do you all care about fire mages being too OP during combust windows? Disc is essentially the fire mage of healers. Bonkers healing during CD windows and useless outside of them.