The only reason a healer would actually *want* Haste rating this expansion is for HoT breakpoints. If you're not getting a HoT breakpoint out of the deal, thus not only getting extra HPS but also making that Haste rating mana-efficient, then you shouldn't put that much value on it.
Holy Paladin Mastery is currently ridiculously overpowered. STACK IT!
The only real question is Crit vs. Haste, and it is and has always been very unimportant for us in MoP, but I do believe that with our Mastery levels increasing (especially when you get enough gear to replace blue gems with yellows!) that Crit will synergize a lot better. Remember that a 206% heal will apply a 206% shield.
If you want to take a look at the extreme side of things, look at what Eloderung has been up to:http://us.battle.net/wow/en/character/lightbringer/Eloderung/advanced
He has always done unusual or different things, and in fact he had basically the same reforging (ignore Spirit/Haste, reforge fully into Mastery>Crit) now as he did back in Firelands haha. But quite obviously he gets the concept of Illuminated Healing being stupid overpowered, and it's pretty interesting that he's leaning on the Illumination glyph rather than Spirit itself. No idea if that's wise at the moment, but it clearly works for him.
On a related note, I'm actually doing some research on Holy against my will it seems. (Between being in the Paladin forums... and quite a few healers in my guild being in the healing forums... haha) I may have to put in the work to update my sticky anyways.