I'm doing like half the damage my fire mage was doing as frost and 30k less than arcane.
Fire is a cruel mistress.
Dependent on Crit+Mastery. You also need to have your rotation completely down. Fireball is complete filler. Don't use Living Bomb on single-target fights at all. Time your Rune of Power with Combustion.
Have a starting rotation of-
Rune of Power+Combustion near the end of it(Combustion is off GCD)
Fire Blast
Fire Blast(You can probably save Combustion till here, to optimize how long you have it for)
Pyroblast
Flame On
Fire blast
Pyroblast
Phoenix Flame
Pyroblast
Fire Blast
Pyroblast
Phoenix Flame
Pyroblast
(By now your Combustion and Rune of Power will have dissipated)
Alternatively, you can fireball until you get a hot streak proc from your fireball and then start the rotation above(Using Fire blast once instead of twice), to get an extra fireblast in for combustion.(I don't do this because....I hate how fire is now.)
Fireball should only be your filler between hot streaks. Phoenix Flame if your Fire Blast is down. Use Flame on once per Combustion, so it's up for your next Combustion(Take Kindling, so that your Combustion comes up faster). If you used 2 Rune of Powers near the beginning of the fight(One with Combustion, one after it), you can use one before your Combustion is up, and another will be up by Combustion(IIRC atleast).
IT's tough, and it's a very tight rotation that can and is thrown off by anything that makes you move.