Dissipation is there for bringing the group back from the brink of a wipe in progression based raids. It is niche and could do with something extra (possibly) but it is by no means useless. It would be better if it gave your group some sort of buff from exploding the fairy, since the healing buff you gain from it is pretty inconsequential and usually not what you use dissipation for.

Sustain on sch however is useless.

But in keeping with the spirit of the thread and maybe not the letter: most useless thing on sch is the enhanced intelligence traits.