Paladins have a lot of situational cooldown tools, no real need to explain most of them here. What I will focus on, is my bread & butter healing rotation/priority system.
Before an encounter, I will be attempting to use holy shock to generate and maintain a three stack of holy power. During an encounter, maintaining a three stack of holy power is always a “nice to have”. I use Holy Power for two things:
(1) Word of Glory (WoG): mana free instant heal
(2) Light of Dawn (LoD): cone AoE heal that hits five (6 if glyphed) targets
(1) gets a lot of use in 5 mans, (2) gets more use in raids, because if it hits 4.5+ targets, it carries more effective healing through to the Beacon of Light (BoL) target (which is usually a tank). I tend to use the glyph that allows a mana free (but not GCD free) switch of BoL, as this is handy in tank swap fights or if *cough* a tank dies. The alternative glyph is the one that boosts mana return from Divine Plea (which I will use on long mana intensive fights). Divine Plea reduces my healing by 50%, which is why I macro’d some party/raid text to its use (telling people that my heals will suck).
I have two ways to generate Holy Power: (A) from using Holy Shock (an instant heal) or (B) casting Divine Light or Flash of Light (FoL) on my Beacon Target. Divine Light is my most mana effective spell in terms of healing per minute, but its slow. FoL is fast, but burns mana. I have talents that allow me to keep one point of holy power after using a holy power spell, and a chance of keeping a full three stack after a WoG cast. Note: in a 25 man raid a Paladin healer would almost never cast WoG, they rely exclusively on LoD which can be almost always gauranteed to hit six targets.
If I have nothing better to do when healing, and I have high mana, I will cast Holy Light, the cheap heal, partly to fish for a proc that will let me cast two Holy Shocks in a row. I do this more often in 5 mans than in raids as raid damage is usually a bit more than Holy Light can cope with.
(1) Holy Shock on cooldown
(2) Divine Light on Beacon target
(3) Holy Light
The major addition to this is Judgement, which does no healing, but returns four percent of my base mana. Judging on cooldown is crucial to mana longevity in fights. So when mana is below 95% and I can use it, I will, unless the situation requires constant healing. One reason why fights go wrong for me, is that if I have to do a long period of healing to keep everyone alive, and there is no space to insert a judgement, then two minutes later at the tail end of the fight I can run dry.
My major “oh crap” button is Holy Radiance, an AoE heal that is centred on me. It also boosts my run speed for four seconds. Unlike other AoE heals, it moves with me when I move. I hit this when everyone in the party has taken damage, or if tanks are low and I have to move when holy shock is still on cooldown and I have no holy power to use. HR can be boosted by using other cooldowns (wings for +20%, and divine favour for more haste ticks and +20% crit). This and LoD are my only spells that heal more than two targets at once – Paladins are still very much single target healers.
Lay on hands is not quite as awesome as it once was, as it does not heal the Beacon target. I prefer to avoid using this if possible, although some fights do require it. Its also an emergency mana restorer, and I do at times blow it on full health healers who are OOM.
The last force multiplier that I have is Divine Guardian, which boosts the next five single target heals I do. This changes my normal priority/rotation, as I just want to cast five Divine Lights in a row. Doing this plus other cooldowns can allow me to do about 600k healing in under ten seconds. Yes, Holy Paladins are filled with win.
Small amount of damage to one target – use holy light in next break in rotation (where holy shock is on cooldown, and I already have a three stack of holy power)
Big amount of damage to one target – use the big WoG I have been hoarding
Small to medium damage everywhere – pop Holy Radiance as a preventative measure to keep health pools up and/or use LoD
Where a DPS takes, and continues to take big chunks of damage (because they got aggro or like shiny fire), their survival if its left up to me is dependent on how lucky I get with holy power generation … I can sometimes get a 100k of healing off in 3-5 GCDs at low mana cost. If, however, I don’t have holy power … the DPS is in trouble. Maybe I can hand of protection them, or use lay on hands, but if they are on cooldown then its a choice between:
(a) Flash of light – fast, mana burner
(b) Holy Light – slow, cheap
(c) Divine Light – slower, biggest heal
I actually tend to go for (c), because if it works, the DPS is taken out of the danger zone. If it doesn’t, I still have mana left for the other three people. I almost never go for (a) as while I might keep someone up they can burn me dry of mana in about a dozen GCDs, and I kinda feel like I should save some mana for the people paying attention to the fight mechanics. When I do use (b), its usually because my hand just twitched on the left mouse button.
Finally, to state the obvious, if I have to choose between saving a tank and saving a DPS, I save the tank. Sometimes this means I do not heal a low health DPS toon for a long time. Once the tank is out of the danger zone, then I can help the DPS out. The risk in trying to heal the dps, is that if they die before my heal lands, there is no transfer to the beacon target (the tank), so when tank health is low, I always try to switch back to direct healing the tank.