Kael and Vashj?Follow

Your gear looks plenty good enough to put out 1000dps although i would definately look into replacing robe and head. Possibly spellstrike head if can afford the mats or the one from hexlord or voidreaver also very good upgrades. The heroic magisters robe/badge robe/spellfire robe would be a nice upgrade. You already addressed the gemming(looks like some green quality gems in some slots). If you keep a hood with a meta slot as a fire mage I would definately go with chaotic skyfire meta(12 spell crit +3% increased critical damage. Possibly upgrade cloak and get a belt of blasting made, which would let you upgrade some other gear while staying hitcapped. The scryer version of that necklace isnt supposed to be so great but i wouldnt get distraught over that the hellfire encased pendant will drop fairly quickly off hyjal trash. Tymbals is good trinket for its base damage but icon would be an upgrade-allowing you to proc it during molten fury helps a lot. The cloak would be a fairly easy upgrade with shadowcasters from early za time chest or cloak of subjugated power.

All of this is just mostly small upgrades that all added together will make quite a difference, but i would definately change the head/robe asap as the crafted ones even just blow the t4 gear away.

The other thing to look at is active casting time. I'm not saying stand in a fire or in lurker's whirl to get the extra cast off but limit your moving as little as possible. One problem I had when we were in t5 raids was just not trusting the healers enough, id bandage when i could and pop health pots all of which uses cooldowns. Sometimes that is good but I tended to overdo it.I picked up a lot of dps just by trusting the others in raid to do their job. Make sure to have combustion/icy veins/trinket ready to proc at molten fury range, so important to get a huge boost to dps.

Lastly if you dont pvp fire i would take the 3 out of impact, the 3 out of improved fire blast, put 2 into arcane sublety, fill out master of elements, get blast wave, and stick last point wherever you want it. The 40% reduction in arcane threat is rediculously good for any aoe fight, and that is mostly what you will be doing in hyjal on trash waves. Arcane explosion spam with low threat will also help on some of the tk/ssc fights.

Sorry its a wall of text but tried to address everything. =)You will have no problem breaking 1000dps but push for the best group setup too, it helps more than anything if you can get elemental shamans/boomkins/shadowpriests in your group.

Dont forget to double dip your 3rd combustion proc with a fire blast. Though fireblast does not belong in a standard rotation. I always use Fireblast after what will be my 3rd combustion proc fireball. Gaining 4 potential crits not 3 off of combustion.
Use Lurker as a gear check. If you aren't pulling 1200-1400 on lurker i'd say your gear or rotations need to be better, that fight has some movement, but overall no agro for ranged. If you aren't pulling that its eitehr cause your gear *which it doesn't look to be that bad* or you have work to do on movement during boss fights. Lastly.
Knowledge: Knowing the fight can easily raise your dps by 200. For progression fights, do your part and know exactly what you have to do, and what can happen to you. If you know whats coming you can prepare better and more readily go all out without wiping the raid.

I only say Lurker, because the fight has no agro tree, little movement. If a caster cant hit solid dps numbers on lurker fight with decent gear, its probably because there movement is all wrong. Which will reflect ten fold in vashj, kael and harder encounters and the player will know that is what they need to work on.

On lurker you can cast while in the water waiting for spout to stack, at the least you want to get your scorches stacked or keep the scorch buff up while in the water