The rationale behind nerfing WHM and SCH?

[Risvertasashi]

The problem lies with WHM mostly. The fact that all they have is heals means that every healer ever will be "WHM plus more."

Not really, no. Other MMOs manage to give healers very different playstyles while still accomplishing essentially the same core function.

Cloning the WHM kit and slapping cards on top of that... it's purely lack of any creative thought from the dev team. And even then, they could simply make WHM stronger instead of... as has been mentioning, giving AST stronger heals AND all the utility.