If you're in a union with the grails for it, +HP and +Healing are really good. Especially +Healing, which raises healing/regen effectiveness by 1.5% per point. So +100 Healing = +150%. That turns things like Cassiopeia's heal from 1200 to 3000 or Andromeda's from 1600 to 4000. Really nice for soloing as long as you can manage the enemy's meter to only allow normal overdrives to happen.

Unless someone in the union decides to be a jackass and shift grails away from +healing and into some ****ING USELESS GARBAGE LIKE +BURST.