Well part of the reason we got it earlier than pld for the early half of games was because we were the second healer class. When sch came out if they would of given cures for the first half of our lvs to SCH before RDM, until 41 RDM would of found itself having an extemely difficult time finding parties.
Giving SCH CURE 5 while under the effect of add. White wouldn't be game breaking it would allow the game to have a decent second healer and would fit since SCH does have a higher skill rating than us and was designed to be closer to a WHM or BLM alternative. Also with the solo part, yes anything we nuke they can nuke but outside of abys most HNM/endgame NM's RDM doesn't typically nuke kill they melee kill such as genbu back when it really was an achievement to solo. SCH could never do this with their weapon ratings and defence capabilities.
RDM was never intended to be a WHM or BLM alternative, and the biggest reason we got refresh wasn't to be a chain casting mage but was so we could be frontlines w/o the need to rest as frequently. The problem was w/o the AOE version of it and haste we became the chain casters that RDM is best known as now.