Discipline priests, moonkin and ret pallies all have the same problem. It's not so much that their chosen spec isn't viable, it's that the other two specs are even more desirable.

I asked this very same question in the original Holy Priest Theorycrafting a week or so ago. Based on the responses I got, a fellow guildmate and I played around with gear, gems, and enchants on our own spreadsheets and he respeced on PTR. With all of current TBC content clear and with 10-man zones not really being our guild's focus (even with Zul'Aman cleared on PTR), we were more looking to see if it was something that would be a raid min/max question come Sunwell.

Our position was that this person would take on the role of buffer/raid healer. This is based on his talent placement and responsibilities. He is in T6 loot across the board, so I understand our test is very narrow-focused. We didn't change any of his current gems or enchants, though we would probably replace a lot of the [Sparkling Empyrean Sapphire] with [Royal Shadowsong Amethyst] and factor in some of the [Teardrop Crimson Spinel] to counter the loss to +healing from Talents. Overall, the gear set would be more geared to +healing and mp5 rather than Spirit. This is because the scaling benefit received from Spirit in a PS spec, is much less without talents like Spiritual Guidance and Spirit of Redemption.

Results from PTR and Zul'Aman so far have led us to believe that this is a raid viable spec. Is it a maximized healing spec? No. However, it does appear that it can offer a raid maximization perspective. The staying power of a PS spec (even in Spirit gems and enchants) is still there. The healing output, in T6 equivalent loot, isn't so significant a loss and will only improve with adjusting gemming. Granted, if you have a person obsessed about topping healing meters, this spec isn't for him/her. To me, this spec represents the ultimate support role. Overall, in a matter of min/maxing a raid, there could definitely be situations come Sunwell where PS is huge.

I don't believe it's a critical spec to have the moment 2.3 comes out. Nevertheless, I do believe some Priests in each guild, should look at the gear they acquire now and take into consideration if they will spec PS come Sunwell. In that regard, at least you're saving some money and guild resources.

Discipline has it's own +5% spirit in Enlightenment, so no real loss there. 25% of spirit ought to be something like ~200 +healing at max or so?

You can't get Spiritual Guidance if you are Pain Suppression spec.

PI could be a big help to Pally tanks. A nearly 20% threat boost for 20 seconds could be fairly useful. Unfortunately, the cooldown limits the usefulness for periodic AoE fights like Solarian or Tidewalker.

It seems to me that 41/20 could be a strong spec for heroic instances, where both PS and PI could find a variety of uses and be available for most pulls. Also, the 15% larger mana pool would be actually be helpful. That said, there isn't really any high end 5 man content, so nobody reading these boards would bother to spec for it.

This is a pretty good estimate, yes. Then again, you can also swap out your gems and such to counter that straight +healing loss. Most Priests that run 750+ spirit, reach that by gemming with +10 Spirit. Therefore, if you regem with +22 Healing and +11Healing/2mp5, you counter much of that loss from talents.

Now, I wouldn't suggest a Spirit Priest regemming if you don't plan on being PS spec, b/c of the changes coming to Meditation and overall the benefits of Spirit. My point was such that if you do chose to go PS, you can have pretty similar healing output and longevity.

If that's not a huge loss I dunno what is...

Assuming you still spec imp DS, you lose 3 points of emp healing, which is worth more than an effective +12% to your +healing (in fact, it is effectively +14% to your +healing value for GH and FH). You lose 10% to all heals. You lose 5% spirit, and ~150-200 +heal depending what your spirit is at. You also lose 6% clearcasts which at a worst case scenario a 6% mana cost reduction to your FH/GH/BH, and a lot more than that if you abuse it with inner focus to go out of the FSR - just inner focus alone wouldn't have nearly that much effect as if you need to cast lots of heals the first free spell just gets you out of the FSR and maybe gives you a tick (if you're spamming you get nothing), while the 2nd free spell gives you at least 1 tick (if you're spamming) and more ticks the slower you're casting.

Seriously the loses to healing are EXTREME no matter how you look at it, and I really doubt any way of using PS and PI can make up for it.

The problem is that in general you have one of three roles in a raid: tanking, healing, damage. I hope we can easily discard the tanking option. Even if discipline gives some amazing buffs (and it does), your slot is still wasted unless you have something to do DURING the fight.

Lets assume discipline is worth spending 41 points on. Where do the other 20 points go? Either shadow for damage or holy for healing. But shadow is horribly mana inefficient without vampiric touch-- it doubles to triples your longevity. So that option is gone. At least with holy you can get some core raiding talents, but you still don't have enough healing power to compete.

Ideally I'd like the discipline tree to have some amazing buffs and enough talents to support reasonable but not exceptional healing or damage. To compete you'd need some serious buffs though. I'm talking "Your spells cost 10/20/30/40/50% less mana" kind of cheap to give your damage or healing longevity that's even in the same ballpark as holy and shadow priests.

The problem is not just the ineffective healing, it's the fact you just don't get enough other features in return. PI and PS just don't cut it as something to make up for the healing loss.

If they were to remove the lengthy cooldowns of PI and PS to enable it to be cast on multiple people, but give it longish cast times to prevent spamming with impunity, maybe discipline could work as a standalone class type?

If a lack of things to do while waiting for spells is a concern, then eliminating the need to wait, or even making spells channeled to force the player to concentrate on the role would be the solution?

You could *probably* make discipline viable by casting PI on a druid who rolls lifebloom on tank all through the fight, then gearing up for high spell crit to keep inspiration on. Pain suppression would on many fights probably be castable on main tank, making druid+priest a reasonably good MT healer combo. Still, it sounds a bit too much hassle for the tradeoff.