SCH needs some real shields, and it's sad how easily it is to do so. Just replace some of SCH's heals with shields. Adlo could lose its healing and simply always give catalyze. Succor could double its potency but only shield, not heal. We can even keep Emergency Tactics, but raise its CD to 30/60s to make it really feel like it's only for emergencies, not some cheap way to stop pretending we're not pure healer when it suits our mood. Adlo and Succor would probably have to become instant casts so that it's not overly punishing for people who haven't memorized fights, but I think that's not really a bad thing. It's already like that for AST's Aspected Benefic.

Lustrate could turn into an AOE regen. And for that matter, make shield healers the regen king, not pure healers. Regen was originally a way for pure healers to reduce their MP consumption, but nowadays WHM is the king of MP. SE doesn't need to keep pretending that regen's purpose is to preserve MP, and instead make it part of the shield healer's identity. Shield healers could be crap at quick healing, but they can put up lots of powerful shields to keep people alive while the regens are working to fix them up. Excog could be an especially powerful single target regen as well under this direction.

This direction would give shield healers a powerful identity that's more than simply damage prevention, and allow the two sides of the role work together in symphony. What's the point of pure healers also being the regen healers if their raw healing is enough to quickly bring up everyone from 25% to 85% whenever they want? Transferring the regen effects to shielders would both allow the two sides to feel much more distinct, but also synergize them better as a team. Shielders handle the front and back of big damage, while the pure healers handle the middle.

I don't know how Sage will work, but if we build shield healers with this sort of role identity, it would give the new healer a nice place to expand into. All the while, as long as the regens continue to stack like before, we can continue to get mechanics like True Walking Dead in casual content, as double shield healers wouldn't be crippled for having to do so much raw healing once in a while.