I have both SCH and WHM so understand some of the thoughts you are having.

Espon is correct with the constant use of Adloquium as that stacked with Stoneskin can prevent a lot of damage.

The thing I love about SCH is that the job doesnt seem to get as much emnity as WHM. In Coil Turn 2 we have the SCH use Succor a lot as it keeps the back liners healed so the WHM can focus on the Tanks.

As SCH, if possible try to get your DoT rotation out every 20 seconds as the damage really helps the fight to progress faster.

Eye for an eye and Virus is super helpful in Turn 1 Last Boss too.