Augment healing adds a bonus to hp healed by conjuration (healing) spells based on their spell level. Also in Unearthed Arcana there was talk about variant spontaneous clerics who if they had the Healing Domain instead of new spells added to their list they got to use d12s instead of d8s for cure spells; a +2/spell level (max +8) would be far from game breaking. d10s actually is better than +1 CL adding +1/spell level (max +4 as 5th+ level ones just repeat in mass effects) to how much you heal.