With your gear you should be pulling AT least 5k in any raid, maybe try focusing more on cooldown uptime and timing with your procs, invest in black magic enchant for your 1h. For example, i usually start the fight, Arcane blast x3, THEN pop cooldowns, so as to have my procs up for trinkets or enchants and giving me as much dps as possible. Presence of Mind is great for gaining a bit more damage when you have 1 or 2 seconds left on a proc. Manage this timing and utilize it as much as possible. Icy Veins and arcane power must always be on cooldown, except when you're expecting a BL or power infusion in the near minute, when you can use both in congruency with said buff. And manage your mana, if you're good you will end the fight with 0 mana but no dps loss because of it.
Edit: I also use Presence of mind and cast arcane blast when i'm at 3 stacks, that is if i already have a missile proc.
Another great tip i remembered, utilize your clearcasting procs, they give you 30% crit on your next spell, and no cost, so if you're x4 stack and get a clearcasting proc, cast again! if you get lucky and you have procs up you can do ALOT of extra damage and spend no mana on this. Be actively expecting for clearcasting procs.