So you're saying "WRONG WRONG WRONG" because you don't see math, but there is no math for yours either. Haste is better situationally hands down.
Specifically what situation? The situation where you read EJ forums and can't think for yourself?
If we assume these shields are 100% effective, Mastery will be less output then haste, but significantly more compared to crit.
That situation? Because I get the feeling that everyone is basing their knowledge off of this sentence, and I believe it to be WRONG.
100 Mastery provides: ~0.697% additional shielding
100 Haste provides: ~0.78% Spell Haste
Or maybe this is the one that gets you? Added absorb shield, a situational use (only useful if the target gets hit AFTER your heal hits), and Haste has a higher percentage clearly... well why the hell not - HASTE WINS!
Except it doesn't. Every point of haste has to be compensated with additional spirit, at a rate I can't currently claim to be good enough at math to pin down. If you include this spirit into the Haste rating bundle (100 haste now becomes something like 85 haste and 15 spirit), you will see that percentage drop to... oh look!85 Haste provides: ~0.653% Spell Haste
15 Spirit provides: effectively nothing, it is compensating for the above
No friggin way! That would make this argument favoring Haste void. Now wait, if that were actually true we would have had someone do the math and find out EXACTLY how this impacts Haste. Except nobody seems to have done so because they are fixed on the clear
downsides to Mastery.
Mastery requires the target to take more damage after your heal hits to be effective. Well... when I think about it this actually happens quite a lot! Assuming it does not, though, what exactly was gained by healing the player faster anyway? Further healing to that player is precursory to damage taken as well, JUST LIKE MASTERY SHIELDING. This is exactly why that argument against Mastery is void.
Mastery adds nothing to Beacon healing, which is the strongest increase to our healing efficiency of course. This means that while Mastery is efficient - 100% actually, it costs nothing but rating which we have yet to establish a clear indication of which stat it aught to be prioritized in! - it has a clear 33% net loss in effectiveness for straight healing output.
This is of course assuming you are using Beacon effectively 100% of the time. Wow, that was a little hiccup you did not see coming did you? How often are you healing targets when your Beacon is at full health? How often are you healing said Beacon target anyway, especially when it is the target receiving the most damage? Beacon is not perfect and even assuming perfection in its use the loss to Mastery in efficiency drops it back 33%, but that is not a loss
it is a GAIN for HASTE (and crit)! Lets throw that number in for Haste instead, shall we?
85 Haste rating: ~0.172% more healing output than 100 Mastery rating