Discipline Priests

[Bolty]

You'll have to be specific about what you feel the problems are. Perhaps post a log or two for analysis.

I'll second what Tuft wrote here. In WoW 5.1, Disc Priests are generally considered the top overall healing class/spec due to a number of factors including fight mechanics, damage output while healing, the power of absorption, and utility. While of course healing meters don't tell the whole story, a quick look over at World of Logs' HPS rankings for Heart of Fear tell a strong tale.

I feel you're unfairly comparing Holy Priest DPS to Disc Priest DPS. Holy DPS is an actual viable DPS spec when geared for properly (not an easy task), but it does no healing while DPS'ing. Disc DPS is a viable healing role where you are actually contributing to keeping people alive while providing your raid with a DPS boost, useful for when you're running into enrage timers. No other healer can touch the DPS power of a Disc Priest while healing.

In 25man raids, when played properly and at equal gear levels, a Disc Priest will consistently top the meter on pretty much every fight. In 10man raids, there's less total domination because of the mechanics of Spirit Shell reaching its absorb limit when there's only 2 groups to heal. But Disc is strong at both AoE healing and tank healing - not the best at tank healing, but still strong.

A Disc Priest allows you to effectively ignore certain raid mechanics that would otherwise be considered dangerous, because Spirit Shell is currently radically overpowered. Any raid-wide damage effect that occurs at set intervals (so it can be predicted) can be essentially nullified by you, and you need to play to that. I'll give a few examples:

1) Blade Lord Ta'yak's Unseen Strike: every minute, the raid has to group up and take a big hit from the boss to share the damage. Spirit Shell's cooldown is one minute as well - funny that! Shield up the raid with Spirit Shell and your raid will barely feel a breeze.

2) Wind Lord Mel'jarak's Rain of Blades: every minute (funny that), he sprays the raid with large damage. Shield up the raid with Spirit Shell and your raid will barely feel a pinch.

3) Imperial Vizier Zor'lok: Force and Verve, while not necessarily coming at timed intervals, can be predicted once you know the encounter. Shield up the raid with Spirit Shell and your other healer(s) will get annoyed when there's nothing for them to do.

The challenge of course is getting the Spirit Shell up before each of these things occur, which requires intimate knowledge of the encounters and a willingness to watch those timer bars like a hawk. If done right, your logs will look something like this - notice the large spikes in Healing Done that occur at roughly one-minute intervals. That is all healing you are effectively "sniping" from other healers and leads to you topping the meter, causing all the current hate from the other healing classes/specs. What is likely happening is that you're missing those possible spikes due to newness to the encounters or unfamiliarity with the spec's strengths. But you're asking the right questions.

Are you building an Evangelism stack via Atonement healing before using Spirit Shell?
Are you then using Archangel to boost the strength of your Spirit Shell?
Are you stacking Mastery (at least until 5.2)? It's your dominant stat, and the advantage there is it's also great for Holy if you want to swap specs.

The Icy Veins guide has a number of inaccuracies. You should never use Heal as a Discipline Priest. Ever. Really. If you need light to moderate healing, get it through Atonement - Smite dem bad guys! You do damage to the enemy AND heal your raid (often the tank) AND gain Evangelism stacks all at the same time. With a five-stack of Evangelism, those are cheap casts that pack a lot of punch. Make sure you have a mod that can monitor your stack well. Its recommendation to use Renew while moving is also poor. Renew should only ever be used if you have literally nothing else to possibly cast - remember that with the Glyph of Penance and Glyph of Holy Fire (highly recommended), you can use both of those on the move to heal as well, along with your level 90 talent of choice.