What can this priest bring to the raid?
A typical raid group consists of 7 healers. That number gets changed depending on the difficulty of the fight you are about to go in as. But do you understand the point I'm trying to make here? Your raid leaders want you! Your guild loves you! So why not give them a reason to take you?
There are 3 impact abilities that priests can support a raid with:
Let's examine the 3 most common holy specs for priests and underline why we would want them, shall we?
The Hybrid (23/38/0)
What is it: This is the Holy and Discipline hybrid spec. It used to be fairly common back before Burning Crusade as the spec of choice. The main goal here is to get improved divine spirit.
Why: An increase in spell damage and healing by an amount equal to 10% of their total spirit can never be a bad thing. Casters and healers will love this. Raid leaders should seriously consider bringing an Improved DS priest. All that juicy surplus spell damage will add up.
Notes: I have no points invested in Silent Resolve. I picked up the 3 in Improved Power Word: Shield instead. I almost never have any aggro problems at all. But if your tank has problems with threat, investing a point or 2 into threat reduction might keep you alive a bit longer.
Don't forget! A dead priest is a useless priest!
The Holiness (20/41/0)
What is it: Circle of Healing is the name of the game. Your goal is to heal groups under fire fast and hard.
Why: Personally, I've never truly realized how awesome the power of Circle of Healing was until I entered Black Temple and Mount Hyjal. With the raid sustaining an overall higher amount of damage from bosses such as High Warlord Naj'entus and Gurtogg Bloodboil, AoE healing has never been more important.
Notes: Again, this is a matter of personal preference. Since we're going for an AoE healing build, it would make sense to increase the range of Circle of Healing with Holy Reach. I tend to skip over Spirit of Redemption. I can't think of a single raid where I've ever made good use of that talent. On the other hand, if your spirit is high enough it might be worthwhile to get. Mental Agility under the discipline tree is a must have. Get 1 free Circle of Healing for every 10 bursts you cast! What a deal!
The Pain Suppressor (41/20/0)
What is it: Also known as the PvP spec of choice, I find raiding discipline priests to be quite rare. It's not that discipline priests are bad. Most guilds have other options.
Why: Pain Suppression and Power Infusion can be excellent in certain situations. Dropping Pain Suppression on an intense fight such as Bloodboil can make life easier for everyone. Unfortunately, those certain situations don't occur nearly enough to completely justify it.
Notes: This is where you come in. I have never touched Pain Suppression but I have seen it in action several times. I'm absolutely positive that there are active raiding Discipline Priests out there. Are there any must have talents that need to be invested in? Are the above 2 specs drastically different? What encounters do they shine the best on and who should they be healing most of the time?
Maybe a better title should have been two Priest specs instead of three.
Which Begs The Question:
What's the best raid spec?
There isn't one. It all depends on what boss your guild is working on.
As my uncle Chef Eatticus used to say, variety is the spice of life! If you plan on bringing multiple holy priests to a raid, check out their talent configuration to help make your choice easier. It can't hurt to maximize raid healing utility. However, if I was your only holy priest in the raid, I would pick up Improved Divine Spirit. It provides a buff that will always be useful. The other two spells are dependant on the situation.
"As simple as it sounds, we all must try to be the best person we can: by making the best choices, by making the most of the talents we've been given."
-Mary Lou Retton
Remember that spec isn't everything. No guild will take you raiding if your performance isn't up to par. It's all about putting in the hard work and the effort to propel yourself past everyone else. Only you can make yourself valuable.