I get the impression that Yoshi sees the healers like this:

WHM/SGE: Entry-level Pure/Shield healers
AST/SCH: More challenging Pure/Shield healers

I don't like this as a design philosophy, but it just feels like they are pushing it, and obviously the healer community wants more nuance to all these jobs regardless of player skill. They are going to leave WHM bare-bones, SGE = watered down SCH, AST is our convoluted WHM with a bit more potential for speed kills, and SCH = the actual shield healer. But the effective gameplay style remains the same 2-1-1-1-1-1-1-1-1-2-1-1-1-1-1-1-1-1 (or just 3-3-3-3-3-3 in AoE situations).