2 months ago I had posted that I thought Light of Dawn was broken (because it only healed for a silly amount of 6k to 6 targets). Boy was I wrong about it being broken. Now that I am full epic (much more INT and SP), my LoD heals for 7800, and about 10.6k crit. Seeing these numbers makes me enjoy using it more, as previously I thought it was broken because we have over 115k health. I use LoD whenever I can, whenever it's appropriate, and whenever I want ..
With that said, I truly believe mastery will eventually be worth having. It's not really worth having now, but Blizz potentially has a reason for doing what they do. I mentioned LoD as an example of something I thought was broken, to absolutely loving it. I think Mastery will grow on me the same way. While it starts at like 10% of the amount we heal (so if your holy light heals for 10k, you put a 1k absorbtion shield on the target for 8 seconds), just think about how much better it will be in tier 13 (probably not 12). The amount of INT and SP we will have by then may make mastery worth having.
I have seen in other posts that it may change to a 15 sec bubble, up from 8 seconds. If that is so, consider the following. If your mastery is up to 18%, and you cast a Divine Light that healed for 32000, a 5700 absorbtion shield will be placed on the target (sort of as good as Disc Priest’s Divine Aegis). It also makes mastery nice for pvp with 15 sec shield. I still think 8 sec was fine though.
I can deal with a 4.5k absorbtion shield from FoL and 5.7k from DL. The current tiny shield it does now is almost useless to me. Moreover, I see Divine Aegis on the meters as a high amount of aborbtion-healing for Disc Priests. Right now Illumination Healing on the meters is like #7 for me (download a new recount if you don’t see Illuminating Healing). So I know the tiny bit of mastery I have now is doing minimal, but still something. With more INT and SP, our mastery will be as strong as Divine Aegis.
And of course, right now Pallys are either doing Int > Spirit > Haste > Crit > Mastery OR Int > Haste > Spirit > Crit > Mastery.... But I really think by Tier 13 (not 12), that people may change to: Int > Haste > Mastery > Spirit > Crit. I believe this for a few reasons. Pallys are starting to have more confidence with the changes to healing and conserving mana better, so haste will surpass spirit in priority. And if you're only having minimal mana issues, than Mastery may even surpass spirit. Additionally, I put crit at the end of the priority because you will still get some crits with a low crit %. But mastery will be like a crit because instead of healing more, it puts a shield on the target that almost makes the heal equally as effective as the chance on crit. But the mastery will do the shield “every time,” which the crit is “not” every time. Crit is one of those stats that you either want to stack or not stack, and I am thinking "not" stack, as the expansion continues.
As a final point, seeing how LoD has improved over 2 months with the increase of INT and SP, I truly believe Mastery has the potential to be a great stat. Furthermore, I predict the same thing for Mastery; it will improve as your INT and SP power increases. Therefore, I predict that by Tier 13 (not 12), that many holy pallys will consider: Int > Haste > Mastery > Spirit > Crit.