I love how you're completely forgetting the second Fire Mage in your raid who's sitting on far less DPS than you despite being similar geared; and on Sha it seems he finally got a decent run in and had comparable DPS.
Yes, fine, you were topping the meters in most of your raids, but you can't claim that your DPS are amazing when they don't consistently rank.
If, by comparison, I take my logs from last night (where I was raiding Arcane) where I was 10 iLvls behind you (485, currently 487 due to upgrades) and I'm playing Arcane on Lei Shi (which is far from optimal) and I wasn't cleaving on Protectors, the difference isn't that great; despite the item level difference.
Oh, and you'll understand what DPS I have to compete with when they can consistently rank on separate fights.
http://www.worldoflogs.com/reports/rt-bxfb6jp8pskv1a5l/ Terrace
http://www.worldoflogs.com/reports/rt-ejlpn9fpv4d6kpcu/ Heart of Fear
The only fights I feel I performed *really* badly on were Garalon (Scorch spam as Arcane is far from good when kiting >.>), Ta'yak where I screwed up on Tornado phase so lost a lot of DPS and Mel'jarak but I'm trying Arcane on it next week as I think it'll work fine with barrage cleave and NT multi-dotting.
I'm not wanting to take anything away from you; you're clearly not a bad player, but at the moment Fire just isn't the best mage spec; else players from top guilds would be playing it, which they aren't.