Shouldn't we be thinking how AST will fit in with WHM or SCH. My understanding is that AST will have the ability to compliment either WHM or SCH much like how SCH and WHM cover each other weakness.

To go off on tangent and start speculating on progressing in the new raid without having a clue about the raid at all is no different to saying two AST or two WHM or AST/WHM combo wil be superior because or X reasons.

Most people with raid experience now do not have actual progress experience. Their experience comes from others who have discussed and over time refined builds and strategies. If anything most raiders have learned to execute the strategies developed by others.

If we look at how raid groups progress you'll see that both SCH and WHM were handling specific mechanics and healing in such a way to maximise healing efficiency.

The whole DPS matter came about once raid groups became geared well and were able survive with less healing. It has been already mentioned that SCH bring a lot of utility to a group but this utility does not come free. The price is a WHM doing the bulk of the healing.