Clunky early iterations
The idea of an ability that consumes mana, has a cooldown, and burns holy power points at the same time is simply not intuitive. Without using holy power points on it, it was far too weak. In addition, there was no way to save your holy power points for a later Word of Glory; the two were tied together. In spite of that, the ability still had a hefty mana cost and cooldown, which further limited the usefulness of the spell. You had to plan ahead in order to get the most out of LoD, and it's pretty clear that the spell wasn't working.
It's no secret that I wasn't a big fan of the last iteration of Light of Dawn. All of that changed after I worked on Lich King on 25-man after patch 4.0.1 and saw how powerful it could really be. Light of Dawn was my most effective heal and literally erased Infest before it could start eating away at my raid's life pools. Its potency was just strong enough to heal the raid back up to remove the debuff, and that was all that I really needed. While it wasn't nearly strong enough to keep people up for more than a second on the Blood Queen Lana'thel encounter, Light of Dawn simply ruled for the LK fight.
Unfortunately, there's more than one fight in the game. Light of Dawn's cone is hard enough to work with, and the fact that the graphic is horribly off from its actual target area is simply insult to injury. Trying to get enough raiders into the reticle to make it worthwhile is difficult on any fight that discourages stacking. The Lich King encounter actually encourages stacking in several places, and so Light of Dawn clearly shines there. On a fight like Rotface, I could really only heal the melee classes with Light of Dawn successfully, even though it was the ranged classes that needed the most healing.
A new, game-changing version
The newest version of Light of Dawn is distinctly different from its predecessors. Now, instead of healing all targets that we aim it at, it actually only heals the targets that are the most injured. It's no longer a raid-wide heal, but rather a surgical strike. They also switched it from consuming mana to consuming holy power, which makes it a holy paladin's second holy power release ability.
I can't help but feel that Blizzard folded a bit on defining this ability's role. The developers clearly stated that they didn't want it to be "just another smart heal," and yet that's what it has been trending towards. I think that removing the cooldown will go miles in making it more usable and will allow for clever paladins to use it in quick succession via Tower of Radiance and Crusader Strike. Killing the mana cost also makes it incredibly usable for us, and we don't have to worry quite so much about abusing our AoE heal to its fullest effect.
The key to the new Light of Dawn is that it now heals five (six when glyphed) injured targets at once, selecting the most injured targets. This is very similar to how the other smart heals work; they target those who need it most. Smart healing is key to ensuring that every drop of healing is effective, and it's something that holy paladins really have no experience with. We can cast this at the entire raid and still be certain that it healed the right people.
A brand-new potency
Blizzard's developers were stuck playing a dangerous game with the old version of Light of Dawn. If they made it too weak, it would be useless when only used on five players in a dungeon. If they made it too powerful, it would simply rule when healing the entire raid. Trying to balance a spell that can be used on one player and 25 players is a very difficult thing to do, especially when it's a spec-defining heal. Rather than try to tinker with the numbers and scaling, they took an alternative route.
Light of Dawn now heals for a ton. While the numbers are going to change based on how much spellpower you have, suffice it to say that Light of Dawn is going to actually move your targets' life bars. Instead of trying to blanket the entire raid with small heals, we can now use Light of Dawn to always heal those people who need it the most.
When combined with other smart heals like Chain Heal, Circle of Healing, and Wild Growth, holy paladins will finally be able to contribute to raid healing. Holy Radiance gives us the ability to counter steadily pulsing auras, while Light of Dawn lets us pull people from the gutter quickly. I know it sounds strange to say it, but having a holy paladin focus on healing the raid might not sound so crazy in just a few weeks.
The Light and How to Swing It (Holy Edition) helps holy paladins become the powerful healers we're destined to be. Learn the ropes in Holy 101. We can help you keep a tank alive, heal a raid when necessary and beat the global cooldown. Tanking is a job, DPS is a craft -- but healing is truly an art.