Simply making healers heal more is not going to solve the problem either because if you take a really hard look at the healing toolkit it is, while incredibly overloaded, utterly bland.

Outside of a few interesting effects like Lillybell, Macrocosmos and maybe Haima/Panhaima they are bog standard "make HP or eHP bar go up by X" spells. They have barely any interaction between each other and are more often than not just fire and forget skills.

So all that would happen when you increase the consistently incoming damage, and bring it closer to WoW's attrition healing, would be that you replace 80 of the 130 boring Glare casts with equally boring Cure/Cure 2/Cure 3/Medica casts.