Why does Synastry exist?

Generate an aetheric bond with target party member. Each time you cast a single-target healing spell on yourself or a party member, the party member with whom you have the bond will also recover HP equaling 40% of the original spell.
Duration: 20s

Cooldown 2 min

How is this useful and how has it not been replaced by another ability since Heavensward, especially after the recent rework?