Holy Paladin Mastery, is it really that bad?

I know that for my holy paladin that I go for Intellect> Spirit> Haste> Critical> Mastery. That set up seems to be the accepted best way to go, but I like to think about other options. Could Mastery end up being our best stat (if we're able to get a ton of it?).

What does it do?
Our Mastery is Illuminated Healing. At level 80 our direct healing spells will give a shield that absorbs damage. It lasts for 15 seconds (as of Patch 4.1), it starts at absorbing 10% of the heal, and increases at 1.5% per point of mastery (also as of Patch 4.1). Essentially this replaced Sacred Sheild for holy paladins, and I find it to be an interesting mastery compared to other healers.

Why is it so bad for us?
There are a few reasons. First, the sheild isn't terribly powerful. Absorbing for 10% of a 7k heal is only 700 damage absorbed, and that's pretty lackluster. Second, in comparison to Haste, Mastery appears to be very weak. To give you an idea, If I have a Shadow Priest, Boomkin, or Elemental Shaman in my heroic group I am sitting around 30% haste. That's right around where my haste was at in Icecrown. Heals are faster, the global cooldown is smaller, and Holy Radiance ticks more often. A lot of positives going on, all at once. Mastery isn't really keeping up.

What to do now?
The buffs to Mastery in 4.1 are going to help it out. Currently it is pretty even with Critical, so I would gague the buff to push it behind haste. I want to see if it can pass haste, and maybe even spriit. If the shields can become powerful enough to prevent us from casting as many heals, then we won't need the mana regen from spirit because we aren't casting as often.

So, I plan to head over to the Public Test Realms. While Blizzard is still testing for patch 4.2, I'm going to copy my paladin, and make a premade one to see how powerful Mastery can be. I'm going to gem exclusively for it, gear and reforge for it, and test my skills as healing with it. I'll be sure to record my numbers on recount, and I'll report my results as soon as I am finished.

Hypothesis
Everything is better when you have a ton of it. I hope to find that with a ton of Mastery you can be completely viable. If I am wrong, well it wouldn't be the first time.