Frostfire is a mage build, not one of the game's specs. It splits its points between Fire and Frost around 
Frostfire Bolt, a spell Forever teaches at level 40 that counts as both schools. Fire's talents make the bolt cast faster and light 
Ignite when it crits, and Frost's make that crit deal 200 %. Around it you play Fire's priority: 
Fire Blast on cooldown, 
Scorch for Fire Vulnerability, and 
Pyroblast once 
Heating Up reaches three stacks. The build scores 795.4 DPS on a one-minute single-boss fight, which ranks 8th of 25 damage specs.
A hybrid build
The talent trees are still Arcane, Fire and Frost. This guide's build on a three-minute single-boss fight spends 0/29/22, with nothing in Arcane. Blizzard's class deep dive says Frostfire Bolt was made for builds that take both trees, but the Frost points pay off only while the bolt is your filler. Against three bosses 
Flamestrike takes over and 
Ice Shards falls to 0.1 % of your damage. For packs, compare the Fire guide, whose builds play the same Flamestrike rotation and, on two and three minutes, keep Arcane Concentration.
Strengths and weaknesses
Strengths
- One boss at every length. Frostfire ranks 8th on one minute, 8th on two and 8th on three, with the bolt as filler on all three.
- Crits worth 280 %. A bolt crit deals 200 % with Ice Shards, then Ignite burns for 40 % of that. That burn makes up 14.8 % of your damage on a three-minute single-boss fight.
- Frost's crit on Fire's spells. The bolt's slow is a chill, so a landed bolt has a 15 % chance to grant
Fingers of Frost, and your next two spells, Fire ones included, take 
Shatter's 50 % crit. It is up 15.2 % of a three-minute fight.
Weaknesses
- Mana on long fights. The bolt costs more mana a second than Scorch. On a three-minute single-boss fight you drink two
Major Mana Potions and channel 
Evocation, and the potion is worth 5.2 %. - Long pulls of several bosses. On a three-minute fight against three bosses the build falls to 13th.
- Short of hit. On Classic's spell table, which our simulator keeps, a raid boss resists 17 % of spells before hit.
Elemental Precision and this set's gear cover 5 % and 3.0 %, and a miss starts no Ignite.
On every fight
Frostfire does best against one boss, at any length. On three bosses it holds 7th for one minute and slips to 13th over three, where it has no Arcane Concentration to pay for 990-mana Flamestrikes. The table below sets the fight for every page of this guide.
Races
On the Alliance side Human wins every fight. Their Sword Specialization is now 2 % crit for spells too, as long as a sword is equipped, and the set's 
Sageblade is a sword.
For the Horde, Undead lead on two and three minutes and on every three-boss fight. Their Touch of the Grave gives a landed spell a 10 % chance, once a second at most, to drain 5 % of your maximum health from the boss. On one minute Troll leads instead, since 10 seconds of Berserking cover a sixth of the fight.
What a Mage brings to the raid
Arcane Brilliance gives the raid 31 Intellect, and the table prices it for each spec on this fight. Your Fire Vulnerability stacks raise only your own damage in Forever.
Arcane Brilliance+1.1 % to 15 of 25most: Stormcaller Shaman +2.9 %
Changes
Frostfire's score on this fight after each update to the simulator or the game data. Updates has the details of each.