Well, the sources of the issues are non-cohesiveness between class and content design and the fact SCH was not really...corrected...when players started pumping out DPS with it back in ARR. Ability bloat plays into this too, because post-50 skills had the risk of being redundant if they had all been heals (which creates other issues like too much outgoing healing accessible to a healer, which then means everything has to deal more damage to balance that out).
The devs really need to sit down and look at what they want to get out of their healer paradigm, decide on a set of rules for their healing classes (and for once stick to them across all levels of design) and then make necessary changes on WHM, SCH and AST. Cleric Stance is more an accessory to the problem, and I feel it comes partly from the fact SCH is not as penalized as the other two healers. At least to my knowledge the fairy's healing potency is not nerfed the way WHM and AST are in Cleric Stance. Granted, I wouldn't have given SCH access to Cleric Stance in the first place and given it its own special stance with its own set of limitations.