That's what they have been made for and what the class is good at. It's all about burst vs sustained. WHM is pretty much burst everything including on damage. A SCH rotation can sustain DPS and their heals do the same. AST is still trying to work out what it's good at which is why they keep buffing various things like it's heals and cards.
From the start all they have really done with WHM is nerf it which shows the developers feel it's OP since it's the primary Healer and can solo heal pretty much anything in the right hands.
