Not to sound like an elitist pig or anything, but what kind of gear are you in, and what is your hit and crit rating at as FFB Spec?

I specced my mage FFB shortly after hitting 80. Heading into 10 man Naxx was right around 1800-2k DPS overall according to recount in heroics and on boss fights upwards of 2500. ..Now in Naxx gear on easily 2k-2300 avg and 3K+ on bosses, depending on boss, etc.

I have seen the numbers Arcane mages post on boss fights, and even the ones who aren't as well geared as I am post big numbers, especially on bosses where we all stand there and cast, but they aren't killing me by a long shot.

You said your DPS went from 1300 up to 1900 in heroics you "run all the time", and it seems to me that maybe you weren't doing something right if you were heroic geared and at 1300 DPS. At 70, I was doing 1200-1400 in Kara/ ZA gear with a frost raiding spec.

Like I said, I'm by no means saying that I am the best mage out there or anything, but your numbers should have been better than 1300 as Frostfire Bolt Spec, and as Arcane, 1900 should be what you are posting on fights with a lot of movement and trash clears. On a boss I'd think you could peg 3k or so easily.