Regarding escapes, as I'm pretty sure any good Darius has thought of, wait for both your lane opponent and ganker to get close, use the spin, get infinite movespeed. With a little knowledge of your opponents, you can predict how the ganks will go and either risk it or not. But, late game, Darius does come out and destroy all. I watched a game where a darius was 1/8 in lane and came out carrying 12/10. Needless to say, his team won. He's similar to Jax, but less mobile. Not a powerful laner, unless fed, but comes out late game as a hypercarry. I beleive Darius is OP. Btw, my mini-wall of text loves you all.
tl;dr: Darius can escape ganks, becomes OP late game, similar to Jax. My baby-wall loves all.