You're stacking haste waaaaaaaaaaaay too early, for starters.
Spec:
Go with this: http://www.wowhead.com/?talent=IEMrcRckVtboZxx0xM There are three points left over to place wherever you choose. Suppression is filled in order to cover the gap in your spell hit. Eventually, you'll want to go with this spec (as you progress into 25-mans, especially): http://www.wowhead.com/?talent=IVMrcRctVtcoZxx0tr
Note that some people like Nightfall instead of Intensity, but due to the high amounts of AoE damage in T5 content, Instensity outweighs Nightfall in terms of actual usefulness. Always, always, always, though, try to spec for Imp. Drain Soul and Destructive Reach for threat reduction. If you're not having problems with threat, your tanks are really freaking awesome, or you're not doing enough DPS.
Gear:
Ok I can see you're not a tailor, so you don't get the benefit of Frozen Shadoweave. Unfortunately, you actually need to drop some of the T4 gear for other stuff (most of it's really not that great anyway).
Helm: Go with the Spellstrike Hood. You're not a tailor, so you won't get the set bonus, but Spellstrike set is BoE.
Neck: Pick up the Brooch of Unquenchable Fury from Moroes if possible.
Cloak: Ruby Drape of the Mysticant (Prince) or Cloak of the Betrayed (Delrissa, MgT). Do yourself a huge favor and get your cloak(s) enchanted with Subtlety.
Robe: Shroud of the Lore'nial (100 Badges) may be a piece to consider for its spell hit, but I never found it necessary, because gems and enchants can cover spell hit.
Bracers:{/i] Vindicator's Silk Cuffs are comparable to your current bracers. You lose 2 crit, 2 dmg and instead gain some sta and int.
[i]Gloves: Gloves of Arcane Acuity (Kael'thas, MgT), Handwraps of Flowing Thought (Attumen), or Gloves of Oblivion (Bladefist, Shatt. Halls).
Pants: Spellstrike Pants.
Boots: Ruby Slippers (Oz), Boots of Incantations (75 Badges)
Rings: Ashyen's Gift (Cen. Exp. Exalted) and/or Fused Nethergon Band (60 Badges)
Trinkets: If needed, use Scryer's Bloodgem for the spell hit.
Main Hand: S2 dagger.
Off Hand: Jewel of Infinite Possibilities (Netherspite)
Wand: Tirisfal Wand of Ascendancy (Shade of Aran)
Enchants:
Helm: You have high enough reputation with Sha'tar to get your helm enchanted.
Shoulders: Get your Scryer rep up to exalted. It's not hard, and far easier than Aldor rep.
Cloak: Subtlety, always.
Robe: +6 stats.
Bracers: You have spell damage, but also, if you need a cheap one, get healing.
Gloves: Spellstrike (+15 spell hit) until you no longer need it, then use +20 dmg.
Legs: Runic Spellthread, or Mystic if you're cheap.
Boots: Boar's Speed, or at the very least, Fortitude.
Gems:
Note: Don't socket for bonuses unless (1) the socket bonus is spell hit, or (2) the spell damage obtained is 5 or more. If you're using epic gems, don't socket for dmg bonuses. I'm gonna list gems based on your current gear, to try to get your spell hit up and retain some damage. Never, ever, ever socket for straight stamina.
Shoulders: 2x Veiled Noble Topaz.
Robe: 3x Veiled Noble Topaz.
Bracers: 1x Veiled Noble Topaz.
Belt: 2x Veiled Noble Topaz.
If you absolutely need to keep blue gems for a meta gem to be active, use Glowing Nightseyes. After you've obtained hit cap (202, regardless of spec), use Runed Living Rubies or Runed Crimson Spinels.
One last note, Warlocks are not mana efficient, regardless of spec. That's why we have Life Tap and Dark Pact.
I hope this helped some.