Yep and I agree with him. HPM is important but to justify Mastery as a superior stat by not exploring every option is lacking. Everything needs to be poked, prodded and tested. This is the joy of theorycraft.
TLR - math makes haste look good, real situations say otherwise
I have tested haste on the beta, and in the current iteration of the game it has proved to be less useful than mastery. Holy Radiance no longer has a HoT component, extra ticks from EF don't matter since either way the gain/loss is negligible and add the fact that SS would provide more healing over the duration anyways. Yes you can use EF on multiple people to make it more worthwhile, but even in 10m LoD should outperform WoG/EF so why waste HP on them( apart from situational stuff ). The only thing haste has going for it right now is the fact that it, as always, provides the best way to counteract high tank damage. The problem that stems from having that advantage is you are stuck with the downside of using a stat that eats through mana we do not have.
Why did we love haste early on in cata progresion? High tank damage and HR spam + extra ticks from the HoT... We had the mana to sustain it and haste synergized well across everything we needed to do.
Later in the expansion with the rising buff, making a switch to mastery was optimal due to the amount of over healing being generated.
What is the problem currently? High tank damage will still exist during Mists progression, but we no longer gain anything worthwhile in respect to extra ticks and we certainly cannot maintain the mana required by haste and expect to see the end of a fight.
You can math your way to haste somehow being the best stat, but the fact remains we do not play the game with pencil and paper, our class( and really all healers) cannot currently support the mana hungry play style haste demands.
I'll believe you tested both haste and mastery on the beta, but I also think that if you came to the conclusion that haste is superior, you either (a) have some crazy awesome strat that I don't know about and would love to hear or (b) simply aren't comfortable healing with mastery as your primary stat and do not know how to fully utilize it.
Math is half the battle, applying the dynamics of real situations is where decisions should be made.