Tank healers, skip to the next QQ! This one is not applicable. This is for bubble-spamming raiding discipline priests.
Let’s look at the stats on our gear.
Stamina, intellect, spell power: More is always better. These stats are on every piece of gear you’ll equip, and they scale with iLevel. As you gear up, you really don’t have any choice – you’ll get higher and higher values of spell power and intellect.
Haste: The hard cap for bubble-spam is 150 haste rating. Since we’re almost always affected by the haste bonus from Borrowed Time, we need only a tiny amount of haste from gear before our GCD hits the 1 second hard cap. After that, haste will only affect the casting time of your long-cast spells (GH, PoH, Penance, DH). Realistically, you get capped at 150 the moment you hit 80. Because of the GCD cap, the value of haste is nearly zero. It’s not actually zero, but the value drops precipitously at 150. To paraphrase my old probability professor (discussing asymptotes), the value of additional haste on our gear is so close to zero that we might as well just call it zero.
Spirit: This is a mana-regen stat. Holy priests get a spell-power conversion talent, but we get only regen. Spirit holds zero value if you don’t need any additional regen; having more regen is just wasted mana. So there is a regen “cap” of sorts. In ToC25 or ICC gear, you should not have significant mana problems (perhaps none at all), so spirit has nearly no value for us. You can’t (and shouldn’t) get rid of it from your gear entirely. But it’s highly unlikely that adding spirit to your gear will change anything about your capacities, even marginally. Another wasted stat. (FYI: I will lump mp5 in the same category here…it’s present on some gear, especially shared gear like rings and cloaks, and it also provides zero value if you do not need mana.)
Crit: Our direct heals can crit: Penance, Flash, Greater, Divine Hymn, and PoH. Shields cannot crit. The heal from the Glyph can crit, but the heal is only 20% of the size of your shield anyway. So crit benefits your shield only 20% as much as it benefits your healing spells. Of the stats listed here, crit is by far the best, although it is gimped by nearly 80% for shield spammers. The more you cast direct heals (like PoM), the more benefit you’ll get from crit.
Ok, so all our gear will have stamina, intellect, and spell power. Then we’ll get two of the three other stats as well – either crit+spirit, or crit+haste, or haste+spirit. Two of these stats have zero value, and one has about 20% of its nominal value.
Contrast this with gear for a shadow priest, for example, who will receive less value from spirit on gear than from crit. But all three stats offer some real dps benefit. None of them are wasted, none are as gimped as crit rating is for discipline priests. And the only capped stat for shadow priests is hit rating.
Ergo: gearing for discipline is currently broken. On gear that’s supposedly designed for our spec, we receive less value per point of iLevel upgrade than any other spec in the game. If there were a piece of gear that had stam+int+double spell power, that would suit our needs just fine. But since that won’t happen, we’re stuck with getting approximately half the benefit from upgrades that another caster gets.