SCH is the best pure healer right now....and the best at not going OOM....and the best at providing damage....and the best at healing two different targets....and the best at main tank healing....and the best at preventing damage. At most Dissipation needs small changes in terms of buffs.
I hardly think SCH is the best at everything; WHM has been given a lot of DPS potential now, especially when paired with their new MP regeneration ability. The WHM in my static keeps up very well in terms of DPS to my SCH, and manages MP very well, almost never reaching empty. I have always seen WHM and SCH fairly equal and balanced, and still find them to be now.