Synastry is a bit op.

[SuzakuCMX]

I still don't understand how to use this Synastry. Can someone explain to me? Thanks

You place it on a target. That target now receives 50% of any direct healing (Not regen , ED, or AoE abilities) you put on any player that isn't yourself or the other person with Synastry on for the duration of Synastry.

Most useful for:
Healing both the MT and OT at the same time
Healing a DPS who is low on health while the tank is still taking heavy damage