Skill level 6 at hero level 25 without any items, ~1000 max hp on casters.
AC with Cure Wounds: 962 heal every 12 seconds, 850 over 39s selfheal
AA with Ethereal Healing: 1500 heal every 18 seconds, cant heal self
Their heal is pretty strong, but they also have two damage/support skills which allows them to really influence battles.
Gale deals good damage and allows somebody to escape until heal is available. Weed is probably not exceptionally strong as it can be countered but can be a nasty surprise when overlooked.
AA has Meteor and root from Familiar.
So the question is how strong should heals be ( full heal on the average hero? what cooldown? Mana cost?) for the points you invest in it and if the other skills should be taken into account when balancing the healing skills.
I think the heals should be reduced somewhat, maybe even turned into a % of max hp if tanks need it.
On a side note:
Undeads lack a good healer. Yak wants to buff Naga heal while Lich needs dieing units to deal which is not that great. And nobody uses the Garg heal and she sucks overall anyway.
![Razz :P](./images/smilies/icon_razz.gif)