EDIT: Minor corrections. Also, recent errata means this build uses 3 rare items (Ring of Free Time, Dice of Auspicious Fortune, and Stone of Spirit). 3 rares in Epic is considered acceptable, but none of them are really necessary anyway. Switch Many-Fingered Gloves+Ring of Free Time for Breaching Gauntlets, if desired (helps with Resist All; not many good options...)
I've seen a bunch of dragonbreath spamming builds lately, so after a while I started to look into it in full detail. Combined it with some ideas from the Blender and some tactics, and it got pretty fun...
Tags: Rev., noLFR, AoE (optionally)
Level 30 Build
Inferno
Revenant (Dragonborn), Sorcerer|Shaman, Ninefold Master, Archspell (Doom of Chaos)
Sorcerous Power (Dex), Companion Spirit (World Speaker Spirit)
Ninefold Master resistance: Lightning
Dragon Breath: Fire, Constitution
Theme: Harper Agent
Background: Arcane Student Who Saw Too Much
FINAL ABILITY SCORES
Str 12, Con 26, Dex 26, Int 13, Wis 15, Cha 10.
STARTING ABILITY SCORES
Str 10, Con 16, Dex 16, Int 11, Wis 13, Cha 8.
AC: 41 Fort: 38 Reflex: 38 Will: 38
Trained skill: Religion
FEATS
Level 1: Hybrid Talent (Dragon Soul Fire)
Level 2: Dragonborn Soul
Level 4: Enlarged Dragon Breath
Level 6: Mark of Storm
Level 8: Draconic Spellcasting
Level 10: Death's Quickening
Level 11: Arcane Admixture (Dragon Breath, Lightning)
Level 12: Cyclone Spirit
Level 14: Arcane Reach
Level 16: Burning Breath
Level 18: Ancient Soul
Level 21: Thundering Breath
Level 21: Ghostly Vitality
Level 22: Superior Will
Level 24: Conflagration Breath
Level 26: Disciplined Talent
Level 28: Sorcerous Flux
Level 30: Controlling Advantage
POWERS
Encounter: Dragon Breath
Utility: Deliverance of Faith, Maiden's Waking
Daily: Doom of Chaos
ITEMS
Arkhosian Scepter +6, Ring of Free Time (epic tier), Belt of Sonnlinor Righteousness (epic tier), Many-Fingered Gloves (paragon tier), Ring of the Radiant Storm (paragon tier), Life Charm +5, Eager Hero's Tattoo (epic tier), Rushing Cleats (heroic tier), Coif of Focus (epic tier), Ring of the Crimson Sun (paragon tier), Zaarani's Solitaire (heroic tier), Salve of Power (heroic tier), Ankhmon's Bracers (paragon tier), Totem of the Harrier's Claws +3, Harper Pin (heroic tier), Wyrmsilk Armor of Resistance +6 (thunder), Dice of Auspicious Fortune (paragon tier), Stone of Flame (paragon tier)
Tactics
Before the encounter, make sure you are at nonpositive HP and have your spirit companion conjured. Also, spend 4 healing surges right after ending an extended rest, so that each battle starts with at least 27 THP from the Eager Hero's Tattoo.
First round: Use Doom of Chaos (choose fire), then spam Dragon Breath (you will have 6 minors: 5 from revenant cheese + 1 from the Ring of Free Time).
Subsequent rounds: Use Dragon Breath 6 times (5 minors + 1 standard).
Dragon Breath can use a square within 2 as its origin due to Arcane Reach. Also, it pushes Con mod squares when it hits due to Thundering Breath (though I'm only going to push 4), then slides 4 (Mark of Storm+Rushing Cleats+Cyclone Spirit+Controlling Advantage), and is a blast 5 due to Enlarged Dragon Breath. When it hits me, I recharge it via Ancient Soul, so I make sure to be in the blast. Diagram:
O x x x x x
x|E x x x x|
F|x S x x x|
x|F x x x x|
F|x x x x x|
x|F x x x x|
O = origin square for blast, E = enemy, S = self, F = forced movement square (path that the push/slide follows)
Each DB creates a zone (Conflagration Breath), so by using the forced movement in this way, the enemy enters the zone 4 times per hit (and takes the zone damage, which deals 20 damage due to Doom of Chaos giving vulnerable 10 fire). Also, the zones stack. Which means that, on the 6th DB of turn 2, there are 12 overlapping zones and the enemy takes damage from each one, i.e. 240 damage each time it enters, for 960 damage per hit.
CA is gained for Controlling Advantage via the Totem of the Harrier's Claws and Burning Breath. I'm not sure where the SC needs to be to trigger Cyclone Spirit (should it be adjacent to the enemy's initial square, or the square that they start sliding from?), but wherever it's ruled that the SC needs to be, that's where I put it.
Also, the first time a crit is scored (after the first round), I use Zaarani's Solitaire to do another slide and get a bunch more damage.
With Sorcerous Flux, I make sure that I always get hit by DB (I can hit myself on a 2). If a 1 is rolled against both targets, I use an AP to DB again as a free action (this is the only thing APs are saved for). I can also recover DB 2/day with the Ring of the Radiant Storm and the Salve of Power...but the APs should almost always be enough.
Dice of Auspicious Fortune are used to help ensure a miss with Doom of Chaos (anything other than a 20 will miss).
If the SC is killed, then I need to use a minor action to bring it back (the damage is completely resisted, so it doesn't matter). That hurts DPR...but it also probably means that the enemy has not actually harmed the party at all, so it works out to practically a stun. As such, the enemy is unlikely to choose this.
The enemy could move around, but the standard assumption for DPR calcs is that they do not. Also, the blast has pretty good range, so shifting is unlikely to get them far enough, and I'd just use the first DB to slide them back into position in the main zone. Worst case scenario, I throw rarity rules to the wind and buy 5 Rings of Personal Gravity (they're cheap) and use one each encounter to lock the enemy down.
Surviving
Taking all these hits will hurt. It doesn't hurt that much...each attack is 3d6+29, and I have resist 30 and insubstantial, so expected damage is 4.5. But when it's 6 attacks per turn, that adds up quickly.
First thing is the aforementioned Eager Hero's Tattoo. That soaks up all the damage from turn 1. Then there's more THP from the Ring of the Crimson Sun, giving me a good 6 more rounds of life...which is not enough. So at the end of that last round, trigger Ankhmon's Bracers on the second-to-last DB (reroll with Stone of Flame if necessary; must hit the enemy). This gives healing, which means we start at 0 when gaining the HP. Then on the last DB, I go back to negative (not too much damage though; I still have 15 resist from the armor + PP + Dragon Soul). I am dazed.
On the next round, save vs. the daze via Superior Will (+5 from Coif of Focus, +1 from background). If it fails, reroll with a +2 via Harper Pin. If that fails, use Maiden's Walking to ignore the daze this turn, then save again at the beginning of the next one.
That should be enough HP to get through 10 rounds. If not, there is also Deliverance of Faith to get a surge worth of THP (1/enc), and also Healing Spirit (1/enc) if I run into big trouble.
Can never fail a death saving throw due to the Life Charm.
Calculations
Actual calculations are all done in the DPR Kings spreadsheet (go to View -> Hidden Sheets -> Inferno; please re-hide afterward). I won't bother writing it out here to explain, but I tried to make at least the attack and damage bonuses as transparent as possible.
Calculations for the AoE were not done in depth at all because I don't think it's as interesting, and figuring out how Sorcerous Flux improves everything is complicated, and it's just generally a lot of work. So I assumed that the damage dealt to the secondary targets was 1/4 of my base damage (because they don't have the fire vulnerability, and they aren't necessarily positioned well to make the push damage them). I think if I did all the calculations it'd end up a little higher than that, but not by enough to make me care.
Simplifications for the single target damage:
1) I assume the very first DB was a hit, to cause OGD and create CA.
2) I assume the enemy always has OGD on its turn (this only fails if every single DB missed on the last turn, and the enemy successfully saved against ODB last time).
3) The damage added by the Ring of the Radiant Storm was approximated by simulating the dice rolls a million times.
There are a number of other assumptions/simplifications made, but those are all generally contained in the Tactics section already.
Single-target KPR: 14.61 (post-MS: 18.30)
AoE KPR: 19.28 (post-MS: 24.15)
I can't really see anything controversial in this build; the meat of the damage is from the fact that Conflagration Breath creates a damaging zone that was unaffected by the zone nerf, and overlapping zones each deal damage as normal, and DB can be recharged perpetually via Ancient Soul...all of that is pretty clearly established. The rest is just fluff for optimizing around that basic tactic.