Abilities on live right now, take Structured Entropy for example, that triggered the mage guilds passive (might of the guild) to increase the next "damaging attack" would not increase healing - fine.
PTS - Now the language is changed, lots of the language indicates it increases spell damage. Take same spell, Structured Entropy - "Grants Major Sorcery, increasing spell dmg by 20%" - this does nothing, NOTHING, for healing. Cast entropy, look at your spell dmg - you will see a 20% increase - yet it has NO effect to your healing.
If you're a Templar - slot a Dawn's Wrath ability and trigger Illuminate, which visually displays your spell power increasing by 5% in your character sheet - yet again though, gives 0 increase to healing.
As a Templar I have test all sources of Templar class ability healing AND resto bar healing, no ability that "increase spell dmg" increases healing potency - why? Yet if I go naked (no weapon), and have 200 spell dmg, my healing gets reduced HEAVILY.
I firmly believe ZOS has poorly coded abilities to behave like the might of the guild passive, and they only affect damaging attacks. Please help healers out and /bug report in game - all healers need the ability to empower their healing ability.
If it's any consolation as a Templar, Piercing Spear passive properly increases crit heals by 10%.
Stands-Strong-As-Snow ~ Argonian Templar DC NA V14
Ytheri ~ Argonian Nightblade EP Thornblade NA V14
Heals-All-Colours ~ Argonian Templar EP Thornblade NA V14
Stands-In-Still-Waters~ Argonian Sorcerer EP Thornblade NA V2