The Huns vs The World argument will never be decided. I'll throw a few contenders out for "best Deity civ for *reliably winning any given map*"
1) Arabia
Well balanced, can wipe out a pangaea reliably, great start bias, great UB, UA, UU, can win easily with any victory condition.
2) Shoshone
They always* have a good start, and since the start is usually the only hard part on Deity for an experienced player
3) Inca
Great growth for science (which means they're great at diplo & culture as well), the free roads are awesome, and the free movement in hills is sick for domination in *any* era. Their start bias and UA also make it very easy to defend early aggression. Great synergy. You're going to beeline construction anyway if you want to survive any start on Deity. How many other civs get bonus benefit from taking the most reliable path?
4) Huns. Yes, Attila is good at any start. Liberty free settler, plant that guy right on horses, if they aren't there, use CBs for your first army and capture a neighbor's city with horses. It's not nearly as unreliable as people think. Get creative.
Why does everyone misunderstand continents? Man, do the math. If you can wipe out a pangaea by t100, you absolutely can wipe out your continent by t100. Owning your own continent with no hate from the other one will result in a virtually automatic science/diplo/cultural win, even if you decide not to wipe out that other continent via frigate/horse archer rush, even if you decide not to win via battleships. And frigate/horse archer rush is easier than you think. War is about production, and when you own your own continent, no one can produce more frigates than you. The AI is pitiful at naval combat. :-D
Beeline Astronomy after the Wheel, raze every city that isn't awesome, make tons of CS allies while you tech up, and destroy everything with Frigates.
The Huns are only screwed if they get a completely isolated start. But wait, "screwed" in this case means "left alone with lots of space to place cities" which on Deity is actually "almost guaranteed victory"... So, they're never screwed. Those production bonuses build libraries faster too.
If I had to pick one of the above... man, it's tempting to say Shoshone. Great start = everything.