Clash-of-clans – Rage spell on healers

Rage spell will increase all troops'es damage and heal, it just won't affect on other spells.

From wiki :

The Rage Spell creates a translucent purple ring on the battlefield that boosts the movement speed and damage of any friendly units inside the ring. In the case of Healers, the Rage Spell increases their healing by a similar amount.

For test you can send a level 5 wall breaker toward some level 7 walls, he will destroy the wall with rage spell but he can't destroy it without the spell.

Spells that can affect your troops will only work together if they are certain types.

Rage spells that are deployed on top of each other do not have a cumulative effect.

According to the Clash of Clans Wikia article on Spells:

"The Rage Spell's effects do not stack, even if multiple rage spells are used on the same location."

"You can stack Healing Spells on top of each other to increase the effect."

"The effects of the Jump Spell do not change if you drop more than one spell in the same area, so be careful not to use two in the same place!"