Just a quick primer for folks unfamiliar with Frostfire and how it plays.
TLDR: Living Bomb, Scorchx2, FFB spam, Pyro on Hot Streak. Refresh as necessary. Stack cooldowns, use Mirror Image to even out your threat early.
You can check out my version of the spec. It’s not quite cookie-cutter, as I drop a couple points in Fire to pick up one in Improved Blizzard, and one in Shatter. In the normal spec, one of those points would go into World in Flames to improve Pyroblast’s crit rate by a couple of percentage points, and the other into Impact for a greater chance to stun. Basically I swap a tiny bit of single-target DPS for a bit more AoE. The core build remains the same, however.
Glyphs I use: Frostfire Bolt, Improved Scorch, Molten Armor.
There are three “main” spells you’ll use in your general rotation.
Start off by casting Living Bomb, normally during the pull. Since it works like a DoT, it doesn’t deal any damage up-front, giving the tank 3 seconds to build up some aggro before it ticks. It doesn’t tick for much at a time, but it does add up. The explosion at the end is quite nice as well.
Follow that up with 2 applications of Scorch. With the glyph, this will give you a full 5-stack of the Improved Scorch debuff (for 10% extra crit). Note that if you have a Frost mage along, you can generally skip Scorching, as Winter’s Chill (applied with every frost spell they cast) carries the same crit buff, and doesn’t stack.
Now that the preliminaries are out of the way, we can start spamming our main nuke – Frostfire Bolt. Watch your timers and procs while you do this.
You want to refresh your Scorch stack before it runs out, and you want to apply Living Bomb after it detonates.
When you crit twice in a row, Hot Streak will proc. At the earliest convenient time, you want to throw your now-instant Pyro. Don’t stop a cast in progress to do this, and certainly don’t let your Scorch stack drop to weave it in. You have a few seconds of lee-way, just don’t miss it, it’s essentially free damage.
(Deep Fire mages may recognize this rotation, as it’s exactly the same, switching Fireball for Frostfire Bolt.)
On raid bosses, you also need to manage your cooldowns wisely. There are two big times you want your cooldowns ready: At the start of the fight, and at 20% boss health. Most raid bosses will last long enough you can use your cooldowns at both times – however if you’re running with an overgeared or extremely proficient group, you may only get one shot. If that’s the case, you want to save everything but Mirror Image for 20%, when Molten Fury kicks in.
Cooldowns you should be looking to stack include: Icy Veins, Combustion, an on-use trinket, Mana Gem (if you have 2 pieces of T7 for the bonus, and need the mana), and (if off cooldown) Mirror Image.
Mirror Image is a little special. It doesn’t increase your damage. Instead, it takes you off the threat table for 30 seconds. After those 30 seconds, you grab all that threat back. Generally the optimum time I’ve found to use it is near the beginning of the fight, just after you’ve loaded Living Bomb and a Scorch stack, but before you start nuking. It gives the tank a full 30 seconds to out-threat you before things become a problem. And they can become a problem quickly if you’re blessed with an early string of crits. Normally that 30 second reprieve will even things out, and you’ll be safe when you come out. If it doesn’t look like you will be (watch Omen), pop Invisibility 3 seconds before Mirror Image ends. You’ll Invis just as you come out, dropping all your threat, and leaving you in a good position for the rest of the fight. Mirror Image isn’t really as important later on in the fight, but it can certainly help even out some of the burst-threat you’ll cause popping cooldowns at 20%.
Gear-wise, you’re looking primarily for Spellpower and Crit. Haste is useful, but not something you should be specifically gearing for. Hit is important (as always) up to the cap. Unfortunately, really good crit gear is hard to come by until you’re doing Heroics and 10-mans, so you’ll very likely get stuck using a couple pieces of PVP gear before then. That’s fine, if sub-optimal.
The lack of really appropriate SP/Crit gear means that there’s a very uncomfortable and awkward phase before you get Heroic-level gear where you’ll be easily out-damaged by any class that can DPS. This is frustrating as all heck, but normal. Stick with it, learn the rotation, work on your LB and Scorch uptime, and eventually the gear will come, and those all-important DPS numbers will start to go up.