I agree SCH is a superior healer for turn 5, but what I do not agree is you saying 2 WHM is like almost impossible.
What I am curious tho, is why you stipulate tanks cant enter conflag? o.o, if I were to run a 2 WHM team, I will always ask the tank to enter conflag, due to the fact that you are able to have two regens on the MT.
I agree that WHM is superior for AoE healing, and SCH is superior for ST healing.
But I guess this is why SCH is generally considered OVERALL superior compared to WHM, since there's not much AoE damage mechanics currently (Only notable ones are Titan and Ifrit Extreme, them exploding nails >_>).