There are several ways to accomplish raid heals. Each depends on playstyle and gear. I'll go over the most prominent styles.
Justicar hybrid - This includes the Shaman/Justicar, Inquisitor/Justicar, Sentinel/Justicar and just about any build that has at least 10 points into Justicar to get Mien of Honor, Reparation, and Doctrine of Loyalty.
Pros - DoL is the best AOE heal available to Clerics. You can reduce it's cost by 30% in the Justicar tree. It hits 10 targets (and since 1.4, it has smart healing) and it has tremendous range. Until 1.5, this would also guarantee a crit which would proc spells such as Serendipity. Since it hits 10 targets, it should still proc Serendipity all the time anyways post 1.5. If you go the Inq/Justicar route, your passive heals through Reparation can be quite substantial depending on how much DPS you do.
Cons - You need to hit things to generate Convictions. So you need the necessary Focus for that level. Instant cast spells or melee abilities are the best to proc Convictions. Any life-based attack will do, which is why Sentinel and Inquistor are the two natural souls to pair with Justicar since they have various Life damage abilities. You don't necessary have to be in melee, a Sent/Justicar has 5 different ranged Life spells that you can use. You also need to manage your GCD accordingly. Lastly, mana efficiency is always a problem with AOE healing. Inquisitor offers Agressive Renewal at 12 pts and Justicar offers Purpose, although you have to melee for that one. Still you'll be quaffing some mana pots until 1.5 goes live. And even past that.
The Warden AOE builds - Basically, this is anytime you put alot of points into Warden (31+ points) and use a soul like Sentinel to complement it. How many points you put into the soul depends on how much single target healing you need and how many oh#@@$ buttons you want.
Pros - You don't need to hit anyone. So you need no focus for this. It's very mobile because most of the HoT's are instants. Used correctly, a 51 point Warden can provide the highest HPS of any other Cleric build. Not that HPS means much, but still. You can provide more single target coverage than most of the DPS Justicar builds. You can do a lot of proactive healing rather than reactive healing.
Cons - It's very very clicky. Ideally, you are juggling putting up 4x Soothing Stream on multiple targets while also using your assorted AOE HoT's and the occasional Deluge on the tank plus some Orbs here and there. You will be switching targets alot. The GCD is your enemy here, so you need to prioritize which spells are more important. Most of the AOE heals of a Warden are HoT's and is poor for reactive healing. Also, the range is shorter and hits less people than DoL. Mana efficiency is again a problem.
Those are the two main AOE heal choices as a cleric. If you want builds and specs then you can always send me a tell or find me on vent and I can walk you through them. Good luck to you.