@Paolo: Planning for Tier 10.

My fine, Discipline-based fellow Priest Paolo has created a thread about gearing philosophy for Tier 10 -- weighing up the benefit of the Tier 10 set bonuses for Discipline against the gains of taking the SP/Crit/Haste bonuses available from non-set pieces.

The post is here, and you should go and read it before reading this post, since this is a direct response which was too long to fit in the comment box under the blog post itself.

No, no, no, no, NO, NO, NO, NO!

It's disagreement time! Or, rather, it's time to persuade you away from the BiS non-set argument altogether.

Non-Tier Throughput

As Paolo says, the BiS non-set pieces have a whole bunch of throughput stats on them, and the set bonuses of Tier 10 are more for a tank healer than a raid-shielder. Paolo also implies in his introduction to that blog post that, since his impression of the fights and assigned role so far in ICC has been shield-spamming, overall it is better to take the BiS non-set pieces if you're filling that role because they provide more throughput.

Here's the problem ... well, here's the first problem, of quite a few, I have to say: which throughput stats do you get by taking the non-set gear? Crit and Haste -- mainly haste. Which throughput stats are nigh-useless for a raid shielder? Those very same stats -- Crit and Haste: you don't need DAPPS if you're just raid-shielding. Sure, as Paolo points out, you would gain 25 raw spellpower, but that's an extremely poor gain for losing the Tier 10 bonuses -- as I will demonstrate in a moment. And what you do gain in raw green writing, Paolo then fritters away by saying "I'll gem SP/Int!". It follows that if the only reason you're gemming that intellect is to make up for lost regen, you might as well take the regen, no? If, with the spirit, you can gem pure spellpower, you actually gain throughput by taking the Tier 10 thanks to the lack of need for intellect in gems.

So, the BiS non-set pieces are only good for tank healing, since their only major gain is in DAPPS -- it's not a set for raid-shielding since it confers no benefit (unless the minor 700-1000 shields from Glyph of PW: S crits count as viable DAPPS). But what good are these stats even for tank healing? The DAPPS bonus is minimal. 80 crit? That's only 2%. When you're in a balanced 25-man raid, you're going to be pushing north of 50% crit already, so that extra 2% is a diminished 1% increase. The haste is fairly decent, but only if you don't have haste in other slots -- and haste in other slots is wholly possible to find.

Tier-10 Bonuses

Furthermore, if you're taking the BiS pieces for the purpose of tank healing ... then why not just take the Tier 10 set, given how the bonuses are more tank-centric? You trade a tiny bit of DAPPS and a large chunk of almost-entirely-useless haste for large amounts of extra throughput, potentially freeing up a trinket slot for other things, an actual increase in spellpower-based throughput, and tank-healing set bonuses. Having tanked fights such as Deathbringer Saurfang and Lord Marrowgar, I can say from experience that Chill of the Throne has been very effective in allowing Blizzard to go down the "Tanks take less damage per attack but get attacked more often" route. This route gives us a Deathbringer Saurfang who swings every 1.4 seconds for 6.6k on plate, and a Marrowgar Sabre Lashing for 10-12k every ~1.7 seconds. This rate of damage makes Penance such a powerful spell that you would be a fool not to want its cooldown reset as often as possible.

Raid-shielding

Yet further, there is never going to be a call for raid-shielding on every single fight. Marrowgar and Deathbringer are two fights on which it is viable -- though I would somewhat dispute the former since, unless he charges you and you're slow to get away, the damage he inflicts while using BOOOOONE STOOOORRRRRRM is not *critical* -- it can be healed over time, or pre-shielded *to an extent* without being zealous.

10-man Raid Shielding vs. 25-man Raid Shielding

Paolo's assumptions of raid shielding are also deeply entrenched in 25-man territory. The 10-man raid-shielder only ever has ten people whom she can shield at any one time, which leaves lots and lots of time for tank healing in the meantime. On hearing this, you may think it a pretty ineffectual argument for taking the Tier 10 pieces for 25-man raiding ... but what about changing your philosophy regarding raid-shielding in 25-man settings? By the sounds of things, Paolo is currently shielding a full 25-man raid, all of the time, with Penances here and there to keep certain useful buffs up on the tank, right? So why not, instead, pick two groups to shield, and tank heal the rest of the time? Then go back to raid shielding when those shields need to be refreshed -- or, if you feel like it, pick two different groups to shield every time you move back to clicking your PW: S binding.

Shadow Moonlighting

Paolo justifies taking Tier-10 Shadow gear rather than Tier-10 Discipline gear (He uses the Helm and Gloves in his pure non-set BiS list) using the following logic: "The throughput stats are better, and I intend to dabble in Shadow anyway, so I can kill two birds with one stone."

This logic, unfortunately, is not sound. If you intend to be competitive in the later stages of Icecrown as a Shadow Priest, you're going to want to get the Tier 10 4-piece set bonus. And if you want to do that ... then you'll be gemming SP/Haste, not SP/Crit, in all your relevant gear. (Haste is only better than Spellpower for Shadow when you have the 4-piece Tier 10 set bonus. I will show this at a later point when I update Anathema. In the meantime, just take it from me that this is the case.) The Leggings of Woven Death, for instance, which are BiS for anyone who doesn't need Hit Rating in that slot (which should be everyone, FYI), would therefore have to be socketed with a sub-optimal gem either for Discipline or Shadow.

This, on its own, might not be such a huge argument -- Paolo only overlaps two pieces of gear in this respect which would be affected by a SP/Crit:SP/Haste clash: the legs and Tier 10 Shadow Gloves... But he also cites the helm. The helm, in which you put whichever meta defines your role. You have to take Insightful if you're healing; you have to take Chaotic if you're DPSing.

What I like about Discipline is that you can overlap gear sets with Shadow, to an extent, because SP/Crit/Haste is, overall, The Way to Go™ for both. However, they start to diverge with Haste's increasing importance for Shadow compared to Crit.

Conclusion

Take your Tier 10 set, dear Disciples. You're going to be useful as a tank healer at some point, because Icecrown's tank-damage philosophy favours Penance very highly -- machine gun healing for machine gun damage.

Although Shadow and Discipline can overlap most of the time in their itemisation, it is far better not to try doing so with your Tier set. The bonuses are unique to each and provide far more than a large chunk of haste. Instead of shunning the Spirit on Tier 10 Discipline, embrace it and work around it: Take two throughput trinkets instead of just the one, or work out which dual throughput+regen trinkets have their budgets weighted more towards the former than the latter.

If you wish to be effective as a Shadow Priest in Icecrown, you'll need a full complement of Tier 10 Shadow. If you wish to be effective as a Discipline Priest, embrace your set bonuses: they are the tank healing boon provided on a set laden with the regen that a raid-shielder would love. If you wish to do both? Well ... you're gonna need a lot of Emblems of Frost, I'm afraid.