My MageFollow

So, you're asking what else you can do, except for spec or gear? That leaves.... playstyle? Spell rotation? Theoretically, you will see an improvement in your dps output by sacrificing some damage and getting +spell hit gear. Spellstrike gear is > T4. Get some +spell hit enchants instead of +damage all the way around. Swap out your +dmg gems for +spell hit. You will see your dps go up.

Your spec isnt that far off actually, you just have a few of the pvp based talents instead of taking full pve route, going to icyveins would help on dps and you will probably want the 2 in arcane sublety once you are doing tidewalker and solarian, and even for hydross. Reduced threat arcane explosion is pretty important in the fights with aoe role.
You said you do not pvp at all so the impact, molten shields, and improved fire blast in fire tree are totally wasted points for a raid build.

If you have the spellfire set though that would have the biggest impact on anything over t4, you will lose some stam and int but as a raiding mage, especially t5 dungeons and below, +damage over stam and int all day long. Spellfire is best set well into t5 unless you are going the route of belt of blasting and some of the new badge gear. Using spellfire set will probably keep your spell damage where it is at or higher even if you replace all your damage gems with hit gems.

Other than that, as the last poster said, +hit capped is most important, and like i said your spec isnt that far off, but if you dont pvp at all i would reconsider the 3 talents i mentions. Deep fire is great raid spec but going either icy veins or clearcasting will make a much bigger difference than the 3 fire pvp talents you have.

Impact is less than necessary because with T4+ level gear, things should be dying so quickly that it doesn't matter. In T5-6 level gear, I can usually take out 6+ melee enemies around my level(unless they silence) without resorting to AE spam.

It's actually pretty easy too. Fireball one twice to ensure he dies quickly. When they reach you, frost nova and run to distance, hit a second one twice. When they all reach you, blastwave and blink to distance(those first two should be dead). Hit another with a fireball and a fireblast(should die). When they all reach you again, dragon's breath them all and fireball one. Nova should almost be up by this point. Now it's just a rinse and repeat. When it's over, notice that you forgot to buff yourself with Molten Armor and get pissed.

That said, Impact is one of my favorite talents and I sorely wish I could have more points in it.