I've been playing a fire mage for about 10 years now, so here's the advice I'd like to offer.
Stack critical strike and mastery for tertiary stats.
Try and use Scorch only when moving, but you can use it to trigger Ignite and Pyroblast! procs. (Pyroblast! with a ! after it is the instant cast Pyro)
Keep living bomb up at all times. Here is a nifty macro I use that casts Living Bomb once, then switches to Fireball. After 5 Fireball casts or the duration of Living Bomb (12 seconds), it switches back to Living Bomb. Or, you can press and hold shift to trigger it to switch to Living Bomb manually should you need to reapply it:
#showtooltip
/cast [mod:shift] Living Bomb
/castsequence reset=12/target/combat Living Bomb, Fireball, Fireball, Fireball, Fireball, Fireball
Pyrocamping. What this is, is saving your Pyroblast! until Heating Up has procced again. Then, what you can do is cast Pyroblast! which can sometimes set off a chain reaction of 3-4 extra Pyroblasts!. Then, hit Inferno Blast to reset Pyroblast! and spread your DOTs to extra targets. Then, after that, you hit Combustion, which fucking resets everything and you get to go apeshit all over again.
Our single target DPS is usually fucking garbage. I don't think that's ever going to change. Don't be afraid to pull large groups. As a fire mage, it's what we're fucking best at. You'll kill 3 mobs quicker than you'll kill 1.
Blink, Invisibility, Ice Block and Mirror Image (if you spec to acquire them) are your life savers. Bind them somewhere. With those 4 spells, there's never really a reason you should die. Ever. Drop the idiot clones, freeze everyone in place with a Frost Nova, Blink, (Blazing Speed maybe?) to get the fuck away and hit Invisibility. Let everyone else die while you chill out in the corner.
Really, that's about all there is to it. Playing as Fire we have a pretty decent amount of mobility thanks to Scorch and it triggering Heating Up and Pyroblast!, but don't rely on it. So don't feel like you have to be a stick in the mud and just stand there and burn one mob down at a time. Dot a few mobs up and feel free to move around a bit.
Scorch is shitty DPS and should only be used when moving, Fireball is a filler, Pyroblast is your #1 DPS spell. Do whatever you can to make Pyroblast! happen as often as possible and it usually comes with Pyrocamping.
Good luck out there.
