Fire is not only viable, but also more fun, and from my experiences better than arcane.
Since you are going from fire to arcane you need to alleviate alot of your hit, too far over cap.
Gear for haste. Abyssal Rune is an awesome farmable trinket, you should get it. You should also craft the ToC bracers, they're amazing. Use frost badges on tier gear first. The set bonuses are a huge dps increase.
Start farming triumphs, you have alot of work to do!
Its great for fire. However, to get the full benefit you need enough crit to get a hot streak within 2-3 casts to have good uptime on the 12% haste proc.
The 4p is just another awesome cooldown.
It's all a matter of play style. Arcane is very fast casts, but it can nom your mana very quickly. Fire is big hits and burns, great on the run too, great AoE as well. It simply doesn't shine without great gear.
I'd give arcane a shot if I were you, I wouldn't go back to it now that im fire (regemming is 'spensive), but missile barrage is one of the coolest (and coolest looking) talents.
Edit about your last comment:
They probably didn't list it as you need T9 first, and frost badges dont really come in fast enough until you're going fairly deep into ICC.