Lilies: Delete them from the game.
Plenary Indulgence: Replace with a 300 potency (or even 200) oGCD AoE heal.
Basically I would like to see both of these completely replaced. WHM plays fine as a whole, but there two parts add almost nothing. This is especially vexing because Plenary Indulgence is the capstone level 70 skill.

The big problem with these two skills is that they cost you GCDs. In order to get a max rank plenary out you need to cast 3 AoE heals in quick succession. Most content never requires you to AoE heal in such a short time frame (more than once in 10 seconds), and the few fights that do are already covered by the fact that you will have a co-healer with you. Both the other healing classes have high potency oGCD heals on short cooldowns, and WHM itself has Assize already. Imagine, if you please, using Cure 3 three GCDs in a row, together with Assize and Indomitability, and decide what point there would be to still throwing a Plenary Indulgence on top of that.

Casting a Cure or Cure 2 in order to get a lily is basically worthless. If I have my off global heals available I'm going to be using those to cover as much as possible, I don't have time to spend gathering lilies and wasting GCDs I could be using for damage spells. Especially since the cooldown decrease is tiny. I need the return from three lilies to be at least worth the 750+ potency of damage I lose over that time period, or it will continue to be a forgettable trait.

As far as Divine Benison goes, it is really strong now and doesn't need any buffs. I am pretty sure it would have had a recast time of at least 1 minute if it wasn't for the lily requirement. As it is at the moment I get about as much mitigation from Divine Benison as I do healing with Tetragrammaton, using both more or less on cooldown.