Advice please . a DPS who needs more..er...DPSFollow

Personal opinion, other may think differently:

As far as I can see there's nothing wrong with your gear, most of it is enchanted, your hit capped for frost as well. It's plenty good enough for any heroic/T4 content.

The only thing I can see is unless the armory is playing up your head isn't enchanted. Get the glyph from The Sha'tar quartermaster (Need revered rep). Also unless there's a decent socket bonus, gem for spell damage mainly. If you want a crit gem, go for a damage/crit rather than pure crit.

Apart from that frost dungeoning/raiding is pretty much frostbolt spam with the odd sheep/AOE/Water Elemental here and there so I doubt it's anything you are doing wrong.

I'd change Poldaran's talent spec by moving one point from Frostbite to Ice Floes, but this depends on the length of fights. I have some fights where I'm able to use coldsnap twice, but I guess it's probably not that handy if all the fights you do are less than 6 mins in duration.

As Sheppardinio said you want to focus more on spell damage than crit at the moment (particularly when it comes to gemming) and you don't have to match the gem colour to the socket colour (unless the bonus is worth it of course).

With damage meters it's helpful if you can see damage done by enocunter (e.g. a specific boss rather than total data) as some classes/specs are better for dealing damage to trash mobs, while others will perform better on bosses. I always think boss performance is more important than trash performance, but maybe that's because that's where my strength lies with my mage.

Therorising what might be going wrong:
1. Your party members out-gear you.
My mage (main) floats around 1-1.1k dps on most instance runs (on overall data), my balance druid and hunter are closer to 600 dps. Perspectives on reasonable levels of dps change as you gear up more, I think when I was gearing up my mage in Kara 600 dps was quite competitive for my guild. Now though everyone (including most alts) have better gear and 600 dps is fairly poor.
To sum it up, if your other party members out-gear you by a lot then your damage output may just be relatively bad, but not generally bad (I had one heroic run where I did 45% of the overall damage, it was still a really good run though).

2. Mana issues/cooldown use.
Make sure you have a fresh stack of mana gems for the boss and use them as soon as it's worth it (i.e. when you've used 2-3k mana). The exception to this is encounters where you may need to use a healthstone instead, but I can't think of any of those at the moment. Also make sure you have mana pots with you incase you find yourself low on mana with both gem and evocation on cooldown (possibly you should pot before it gets that bad, but I'll confess to being a cheapskate). Rejuv pots may be a cheaper alternative if gold is an issue (my holy paladin used to use unstable mana pots when we started kara so that I could chain pot without worrying about cost).
Once the tank has a good threat lead (I work this out as 'if I crit will I pul agro?') and you have 5 stacks of WC up it's time to pop trinkets (damage increasing ones affect your WE), Icy Veins and get the WE out.
Try not to do this just before a silence/aoe is going to happen (get deadly boss mods or bigwigs to help with timers for raid bosses). Try to maximise cooldown use for a time when you'll have uninterupted frostbolt spamming.
I usually cold snap straight after the first cooldown use (unless I'm likely to need 2 iceblocks - in which case I'll save it until after the first IB) and then use IV when it runs out and WE when that dies (try and work out a macro to dismiss your WE when it dies or you could have summoning problems). Keep an eye out during the fight for trinkets and IV coming back off cooldown.

3. Buffage.
Make sure you use food (spell damage generally, stamina if you need the health), weapon oil (brilliant is nice - but expensive, wizard is good and should be cheaper) and flasks/elixirs depending on where you're going (remember you can get unstable flasks for use only in Gruul's Lair), I tend not to use flasks/elixirs in heroics or Kara but again I'll refer back to the cheapskate point I made earlier.

Last point: If it's overall damage and you really want to 'win the meter' then make sure you a) don't go afk - this will seriously impact your overall damage, b) hope your tank doesn't like crowd controlled mobs, c) finish off low health mobs with a fire blast or switch target if your FB is unlikely to land before someone else kills it - if the cast is travelling when the mob dies it won't register any damage, d) if you're feeling really cheap then also fireblast any critters you see lying around.

Thanks Sheppardinio, I'm going for the Glyph from the Sha'tar quartmaster, correct. Also after Sublety on my cloak. Yeah,when I respecc I'll getting the WE - someone told me it was a PVP talent! (Thinking about it, at the moment I have aRCANE Fortidude - this could be a PVP talent though, right).

I think according to this you might be holding yourself back a bit because you're worried about pulling aggro. Heck, at 66, I was pulling aggro off the 70 tank a lot in a reg 5-man.

One thing you can do, is wait a little before you start going all out (though many are against this because by the time you start casting the mob (for trash) would be close to or already dead). The way I dealt with my above situation was popping ice block to drop my aggro and start back at the bottom again. It helped a lot for me. But as I don't have any end game experience as a mage, I can't really help out much more.

Ice block doesn't reset your aggro. It makes you an invalid target for the duration, meaning the tank has a moment to deal with the mob without it trying to eat you. As soon as you come out, if the tank hasn't built enough threat, you make one single point of threat and the mob will come to eat you. And now there's nothing you can do about it.

=P I keep confusing it with something else. Didn't mean it that way. Thanks for clearing it up lol

Yep invisibility is the one to use before you pull agro, iceblock is the one to use when you pull agro so you can sit safe and watch the mob kill the nearby warlock, moonkin or healer (erm, did I say that out loud?).

Tank threat can be an issue for dps, particularly if other classes have easier agro dumps (i.e. hunter) or can spread threat out via dots (i.e. warlocks). Either start off with icelance or R1 frostbolts (note: downranking is being nerfed in the patch/expansion), but the time you've stacked some WC the tank should have a solid threat lead (though I have pulled agro off a tank using R1 frostbolt, having waited for 3 secs...), you need to keep an eye out for crits though. Also don't worry too much if you pull agro when the mob is nearly dead, as long as you'll kill it before it reaches you (and if it can be slowed then you should) then it's not a huge deal (though some tanks get very upset about it). Just to clarify, I'm talking 5% health left on a normal elite mob, rather than kiting it from 50% to dead.

And as Anobix said, frostbolt is what you should be using most of the time in instances. Ice lance is only worth using on frozen targets, but generally in a group your FN/frostbite will break before you can cast icelance because of other party members damage.