Word on the street is Illumination is going to be "toned down" to make paladins less effective.
So how about this, paladins receive a fourth heal that negates Illumination while it is in use, or for a short time after it's use.
For example, lets make up a spell, a HoT:
Rain of Light - Light rains down on your target, healing 1850 damage over 20 seconds. While Rain of Light is active, Illumination can not trigger.
Or maybe an AoE spell:
Burst of Light - Light burst from your target, healing the target and up to 4 friendly party members for 958 to 1058. After Burst of Light, mana received from Illumination is reduced by 50% for 30 seconds.
Abilities such as these would give paladins more tools to heal, but at a cost. Not only would the cost of these abilities "tone down" illumination, but it would add a new layer of complexity to paladin healing, making healing a more fun and enjoyable experience.