does SCH gets better aoe heals at higher level?

[Rawrz]

I think part of it is that your timing as a SCH is a little off.

WHM and SCH function differently:

WHM is a reactive healer. Damage happens, you heal it.
SCH is a proactive healer. Damage is about to happen, you toss shields.

You need to know the fights well enough to realize there's a big attack coming and to put shields up before it hits. It does no good to shield after the fact. Even trying for the shield while the boss is casting can be too late if it's faster than you are... unless you {Swiftcast} it.

In the AoE case, this is how it plays out for WHM:

Boss health hits 51%.
Boss health hits 50%.
Boss does AoE attack.
Health bars drop.
WHM -> {Medica}

For a SCH, though, the optimal order is different:

Boss health hits 51%.
SCH -> {Adloquium}
Boss health hits 50%.
Boss does AoE attack.
Shields absorbs damage from attack.

You should set a focus on the boss so you can watch the cast bar.

Whm: damage is about to happen, precast cure II/Medica so that it goes off just after the attack. Great WHMs master this. This is for higher end/familiar content with scripted mechanics.

SCH: You did this one right in my book. damage is about to happen, cast as soon as you can. Shields take an extra second to absorb damage, so you need to get them off at least a second before the attack lands.

Totally endorse focus target its amazing.