There are some rare situations in which you need a very big shield. Dissipation+Fey Illum worked well for this, alongside Mantra, Defiance and Convalescence. Largesse could add to this function in order to boost healing to more than 200%. Either that, or make it so dissipating Lily isn't needed.

In the end, the devs are adamant about Dissipation being an emergency button, so I guess that's gonna be its use going forward, as situational and unused as it already is.