I have a couple tweaks on Shax's build that will make it more viable (this is what I currently run, and it is awesome). This build is capable of solo-healing 6mans and will have you near (or at) the top of the dps parse even in a very good group if played properly.
http://joharaoc.eu/feat?link=v2_1182...f7c42f56d2f378
The two main differences are skipping divine lance and adding points into improved purification of mitra. If you are not running light of mitra or other mana-regen feats, divine lance will simply suck your mana too quickly to make it viable. By adding two points into improved purification of mitra, your two dots (purification of mitra and cleansing fire) have the identical cooldown, making it super easy to keep both up.
The spell rotation is roughly as follows:
For single target fights: rebuke, cleansing fire, wave of life, MSE+insta smite, and then spam smite and rebuke until holy storm is up for the fast-cast condemnation. Once cleansing fire and wave of life come off cooldown, immediately recast them to keep both dots ticking and to keep your improved damage stacks high (from spiritual feedback and holy vengeance), and basically restart the rotation. But do not cast MSE if cleansing fire is not ticking on the target, as it will not trigger the insta smite, which is what makes MSE worth it. Work in repulse when it is off cooldown. If the tank is having problems surviving or holding aggro, throw blessing of mitra on them (also gives you 25% increased magic damage, so it is a very nice damage burst). Work in green heals if the tank is going down fast, and throw your big heal when needed. Use holy cleansing sparingly (usually last 15% of the boss) unless your tank is very good, because you will have a good chance of pulling it.
In multi-target fights: Always target the add farthest away from you, and line them up in a column if possible for additional splash damage. The spell rotation is identical, except you want to spam lance, smite, and rebuke while waiting for holy storm to proc and for your dots to come off cooldown. Lance gives splash and column damage, so it is one of our best aoe spells.
No matter what the fight is, spellweave as much as possible. This is a very mana-intensive build, but there is a 15% mana tap buff in spellweaving that really helps maintain mana. The additional damage is obviously nice as well. Poms also have an incredible ability called mitra's thunder that gives smite and rebuke a knockback effect--great for cc'ing adds.
Obviously, go for scarlet circle gear until you get T4 (but get the yellow priest hands). Pick up steadfast and shimmering and keep decisive and pressing slotted. Empowered mending is excellent too.
Hope that helps.