Health:

• 10 Man - 9.7M
• 25 Man - 34.9M

Abilities:

• Call Blood Beast - Saurfang calls forth 5 (2 in 10 man) blood beasts every 30 seconds
• Blood Link - Saurfang gains Blood Power from damage he inflicts with abilities and summoned creatures.  Instant
• Blood Power - Saurfang grows 1% larger and deals 1% more damage for each point of Blood Power he has.  Instant
• Mark of the Fallen Champion - Deathbringer Saurfang's melee attacks splash to the target, inflicting 3800 to 4200 additional Physical damage. If the target dies while under this effect Saurfang is healed for 5% of his total health. (20% in Heroic) This debuff is casted on a raid member each time Saurfang reaches 100 Blood Power. (gains 1 Blood Power per tick)
• Rune of Blood - Saurfang leeches health when he performs melee attacks on targets marked with Rune of Blood. Leeches 5100 to 6900 health from an enemy target and heals Saurfang for 5 times that amount (gains 1 Blood Power per hit)
• Blood Nova - Blood explodes outward from a random enemy target, inflicting 10000 Physical damage to nearby enemies.  (gains 2 Blood Power per target hit)
• Boiling Blood - Boils the blood of an enemy, inflicting 9500 Physical damage every 3 sec for 24 sec, up to 6 players in 25 man (gains 1 Blood Power per tick)
• Cleave - Inflicts 110% of normal melee damage to an enemy and its nearest allies, affecting up to 3 targets. Melee range. Instant
• Frenzy - Saurfang goes into a frenzy, increasing his attack speed by 30%.  Instant (occurs at 25%)

Blood Beasts:

• Thick Skin - The thick skin of this creature reduces damage from area effect attacks by 75%

The Fight:

First thing to note is Blood Power, this is the main thing the mechanics of the fight center around.  Each ability that hits will making him gain more Blood Power.   The better we're at, at preventing him from gaining Blood Power, the easier the fight is.

This appears to be a 2 tank fight, Thorim style tanking, but not a tank gib buff.  He will cast Rune of Blood on the tank, and subsequent hits will make him heal himself, and gain 1 Blood Power per hit. 

The raid itself is suppose to spread out, preferably the ranged should keep a 12 yard distance from each other.  For as long as there's enough ranged, he will cast Blood Nova on them (like Shadowcrash targets).   Each person hit will give him 2 Blood Power.  Spread out to minimize this.

He will throw out DoTs called Boiling Blood.   These will just have to be healed through.  Up to 6 targets at a time, also each tick will give him 1 Blood Power, no stopping these (except maybe Bubble/Block?).    A shield that can fully absorb the tick will prevent Blood Power gains

Every 30 seconds or so, he will summon 5 (2 in 10 man) Blood Beasts, they are to be kited and never touched.   Each hit they do will give Saurfang 1 Blood Power.   Use hunter traps, totems, hurricane, typhoon, thunderstorm, etc to kite and keep them off people.    They cannot be AoE'd down as they have an aura reducing that type of damage by 75%.   Single target, focus down asap.

Anyways, with all that Blood Power happening, here's why you want to prevent him from building it up.  At 100, he will use Mark of the Fallen Champion, which appears mark one person doing damage to him each time he hits someone (the tank).    He must be healed and survive, or Saurfang heals.   Also, each tick of damage will give him 1 Blood Power.   This also appears to last til the end of the fight, meaning, mulitple Marks will occur on several people as the fight goes on.    Which also exponentially increases his Blood Power gain rates.    This in turn is the soft enrage to this fight.   As too many people get this, it'll just build up way too fast giving more people this and people will start dying and healing him back to full health, etc.   Also, the mark persists through death, so brez's are not recommended if they die unless you're really on the ball with instantly healing them.

A final thing, at 30% hp, he will Frenzy, appears not to be tranq'able thing, more of a low health enrage.

In the end, the fight is "simple" in concept, but can be brutal to healers and can fall apart easily.

Achievements:

I've Gone and Made a Mess - Defeat the Deathbringer before Mark of the Fallen Champion is cast five times in 25-player mode (3 in 10 man).

Just be good at avoiding gaining Blood Power and or have high enough dps to zerg through it.