Uh, what the hell is the problem with solo-healing? It usually just means you out-skill and/or out-gear an encounter, and honestly it's great to have all that responsibility, I often offer to solo heal large parts of a fight (and still find time to spend in Cleric) because I enjoy doing that. I also don't know why your solution to this includes nerfing Cleric. If a healer can truly solo-heal a fight, you don't bring another healer in Cleric, you bring an actual DPS job. Otherwise it's just the regular main/off healer dynamic that this game has had since quite a while now, and which is something I really enjoy about it.

Also, as others have pointed out, your "DPS healer" is literally a description of how a (good) SCH plays. If anything, the game needs another off healer to compete with SCH (and it better be DNC!), since WHM and AST - in both sects - are primarily designed as main healers and don't really compete with SCH for a raid slot.