I disagree in how flexible AST really is. It's more "fill in the hole" than it is "flexible". AST can be the WHM or "SCH" if one currently isn't available, but it can't switch mid-battle. These changes would allow the SCH to switch mid-battle, having the ability to control their shields and regens by which fairy is active and what Tactic was used before their trademark spells. This would also leave the door open for a true, pure "shield" healer (the true opposite WHM, having strong shields attached to recovery spells and a large, on demand, HP-percentage based Shield that the WHM used to have, and nice oGCD healing, but almost no regens except for a cooldown or two and very little support [and probably really high personal DPS]).
If it being the "DPS healer" is true then there are a few problems with that philosophy. 1) How much DPS vs healing do they bring that warrants their inclusion rather than a real DPS? There is no way a healer should do more damage than a DPS. It's hard to justify SCH DPS in even high-end content except v4S when a WHM can brute force most of the healing on its own. 2) If they were true DPS healers, then their DPS kit would have more interactivity with its healing kit, but it doesn't. Both WHM and AST have oGCD skills that is/can be a heal and damaging ability (Assize for WHM and Earthly Star and Minor Arcana to a lesser extent) whereas the DPS and the Healing aspects of SCH's kit are kept completely separate (except for Energy Drain, but that only heals the user unlike the other two skills I mentioned before which heal the party or target). Being the DPS healer was a lot more true when Cleric Stance existed as a Mind/Intelligence swap rather than a pathetic Raging Strikes since the fairy covered a lot of what a SCH needed to heal, allowing their DPS uptime to be really high for a healer. With the fairy being so weak now and SCH's heals so expensive and the shields are almost unnecessary except for a few cases, that's not really true anymore.