Let's do the numbers
I realized that I was going to be trading intellect for haste at roughly a 1:1 ratio, as I had already reforged all of the secondary stats on my gear to haste and was still short. After dropping a Dragon Soul-quality intellect trinket for Bottled Wishes and changing out several of my gems, I lost upwards of 750 intellect. That's roughly a 10% hit to my intellect pool, which is a major blow. It's also much more than I expected to lose, but that's because I sort of rushed into the project without much planning.
What I didn't fully account for was the loss of Maw of the Dragonlord. I knew I'd be losing the sweet mini-Light of Dawn proc but forgot that it was making up about 6% of my total healing on some encounters. I swapped to my heroic Vagaries of Time for the extra haste, but losing the Maw proc wasn't worth it. I would've had to squeeze another 175 haste out of my gear to have both 3,500 haste while using the Maw, and that would've required dissolving my epic intellect gems. I'm willing to spend some resources on an experiment, but not when it starts costing me tens of thousands of gold.
There are five ticks
The obvious upside to having 3,500 haste was seeing a significant boost in the amount of Holy Radiance ticks blanketing my raid with healing. Even though I cast a similar number of Holy Radiances, the tick count with the bonus haste was much higher. I felt like my Holy Radiance was stronger, especially on heroic Ultraxion, but that could've just been my imagination.
If I were just trading some mana and the Maw of the Dragonlord proc for the extra Holy Radiance tick, I might consider keeping my haste set around full time. The extra ticks did boost my healing quite a bit, but only on fights like heroic Ultraxion and heroic Yor'sahj, where I'm spamming HR quite frequently. On other encounters, like heroic Morchok, Holy Radiance only saw infrequent use, which makes a haste set pointless.
No mana problems
I didn't run into any mana issues while running my 3,500 haste build, but I was never close to running out of mana before. I know that I obviously regenerated less mana due to missing all of that intellect (which affects our Divine Plea, Replenishment, etc.), but it never stopped me from casting whatever spell I wanted to. This could be due to the fact that my raid is pretty disciplined and takes minimal damage already. I did run into a small bit of mana trouble on heroic Zon'ozz, but that was due to my raid's priest swapping to disc and his group subsequently missing a Lightwell.
The real killer: spellpower
The truth is that while the HoT from my Holy Radiances helped improve that one spell, all of my other healing spells fell in potency. I didn't account for the massive loss in spellpower due to the missing intellect, and that's what hurt my healing the most. Sure, I was getting an extra tick of Holy Radiance, but each tick healed for less. The initial Holy Radiance heal was down almost 10%. My other healing spells were all weaker as well.
The combo effect of losing my Maw of the Dragonlord (6% of my healing) and nerfing most of my other spells by 10% resulted in my HPS staying put, even with 3,500 haste. In some situations, my HPS actually went down. I spent all that time and effort focusing on a single aspect of my healing arsenal, and the rest of my spells felt the blow.
Haste is still a good stat for holy paladins, but not at the expense of intellect. I don't mind sacrificing critical strike rating or mastery rating at the altar of haste, but we simply shouldn't mess with intellect. There's a reason that holy paladins are so attached to it. If I could rebuild my set to reach the 3,500 haste plateau without cannibalizing my intellect, I would do it in a heartbeat. As it stands, I'll need more heroic gear and some new haste-laden jewelry before I can make that happen.
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