WHM getting progressively more unnecessary in content?

[Yeol]

Also there has been little to no evidence presented that prove that WHM aren't the weakest healing job currently.

Correction, they are not the weakest. They have no party utility like the other two healers which made them less desirable.
The weakest in heals will be SCH > AST >= WHM (Strongest heals).

Proof will be FFlogs. Someone posted numbers between WHM and AST comparing healing numbers and party HP%. WHM is superior but AST is not far behind.