why is darius allowed to 1v5 with a black cleaver and 5k hp?

because he was level 17, 13/3/9 with 6 cs/m, and outside of nocturne, you were all squishy and 2-3 levels below him. Diana was more fed than he was, but she went basically straight damage.

Because he wasn't kited?

Why does your team have no cc or kiting potential? Why did you stand in the radius of his q? Why didn't you run once you got low? Why is the sky blue?

xd

Because he knows what he's doing.

because he is Darius, The Potato Masher.