Sch spam is not just 1 heal
It's Adlo, Phys, Adlo, Phys
When tank is full hp use 1 Adlo on him

Fairy can heal the party
When tank taking heavy dmg use Rouse (pet buff) for strong pet heals
Place fairy in a good spot, don't turn her AI off, let her heal the pt while ya focus tank

Virus boss for oh shit mom. maybe throw sacred soil if a lot of aoe
Never use Sacred Soil, but know the few situations when it should/can be used

Use up Aether stacks just before Aetherflow goes off cd
Use em on Lustrate (sometimes energy drain, almost never on sacred soil)

Not sure who told you not to Lustrate, but Lustrate is something you can use almost freely.
The way you gotta use Lustrate, is: keep holding onto it as long as you can only use it early if needed, once your Aetherflow has only 10-20 seconds of cd left use Lustrate whenever for whatever
This way 3 new stacks will be ready soon