On a one-minute single-boss fight the Discipline healer runs 34/17/0. It goes deep enough into Discipline for 
Power Infusion, taking 
Meditation, 
Mental Strength, 
Penance and 
Divine Aegis on the way, and puts the rest into Holy for 
Divine Fury, 
Holy Specialization and 
Improved Healing.
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0/1005203030325101531-0350500301 · Horde (Troll) plays Tuned 33/18/0 b: +1 Inner Focus, +2 Improved Healing, −1 Mental Agility, −1 Improved Inner Fire, −1 InspirationEach fight, faction and build has its own searched talents. They differ by a few points, mostly among the talents worth nothing in our sims, so the reasons below hold for all of them.
Why these talents
Meditation lets 50 % of your Spirit-based mana regeneration continue while you cast, against 15 % in Classic. A healer is always casting, so without it your Spirit does almost nothing. It is worth 11.5 % of your healing on a three-minute fight, and 0.5 % on one minute, where the fight ends before your mana does.
Improved Healing takes 15 % off Heal, Greater Heal and, in Forever, Penance. Those three are almost all of your casts, so it is worth 10.0 % on three minutes. On one minute the builds keep a single point, because mana doesn't run out there.
Divine Fury cuts half a second off Heal and Greater Heal, from 3 to 2.5 seconds: a fifth more casts in the same time. It is worth 6.1 % on three minutes and 13.1 % on one, the build's top talent there.
Penance is a two-second channel of three bolts, each 425 plus 19 % of your healing power, every 12 seconds. Its 385 mana buys more healing than any rank of Greater Heal. That makes it worth 3.2 % on three minutes.
On one minute it is worth −0.8 %: with mana to spare, Greater Heal heals more per second of casting than the channel does. No screened rotation leaves Penance out, so the one-minute rotations still cast it. If you know a fight will end before your mana does, Greater Heal is the better cast.
Divine Aegis turns 15 % of every critical heal into a shield on the target. We count that shield as healing when it lands, as we count every shield, since nobody takes damage in our fights. It is worth 3.9 % on a one-minute single-boss fight, where nearly all your healing comes from direct heals that can crit.
Mental Strength adds 15 % Intellect, which means a bigger mana pool and a little crit. It is worth 3.6 % on three minutes.
Power Infusion adds 20 % healing for 15 seconds every three minutes. Our priest casts it on itself at the pull, where it is worth 5.1 %. It is the reason the build spends 30 points in Discipline.
Flexible points
About a dozen Discipline points are worth nothing in our sims. They are the price of reaching Penance, Divine Aegis and Power Infusion, and the row requirements decide most of them.
Improved Power Word: Shield, 
Soul Warding and 
Renewed Hope. No searched rotation casts Power Word: Shield (see the Rotation page), so all three are worth 0.0 %. In a raid where the tank takes damage, they are what makes you a Discipline priest. They give a 20 % stronger shield with no cooldown and up to 10 % crit on your heals to a shielded target, so keep them.
Silent Resolve and 
Improved Inner Fire. Threat and armor, worth 0.0 % here. Take Silent Resolve if you pull threat from the healing.
Inner Focus. It reads 0.0 % because our priest wastes it at the pull (see Cooldowns on the Rotation page). Used on a Greater Heal, it saves the whole cast's mana and adds 25 % crit, so take it.
Inspiration. Two or three Holy points to reach Improved Healing. Its armor bonus after a critical heal isn't modelled, so it reads 0.0 %, but on a tank it is the best place for them.
What each talent is worth
A row's number is the healing this build loses when that talent's points are taken out and nothing else changes. Talents lean on each other, so the rows don't sum to your healing. To place one spare point, look at the "last point" column: it is the cost of taking just one point away.
On every fight
The builds for other fights move a point or two at a time: Inner Focus, Improved Inner Fire, Renewed Hope, Inspiration, Mental Agility and, on some three-boss fights, Improved Renew or Divine Fury.
The one-minute builds also drop Improved Healing to 1 point, since mana doesn't run out there.
The table sets every fight's build beside this one.