Blade wins . . .
1st Blade will react much faster than Darhk can observe.
2nd Blade does have a ranged weapon . . . his swords!
3rd Darhk has never (as far as we know) faced an enemy of Blades strength or speed. I'll give Darhk that he has faced and probably is more skilled in h2h combat than Blade - but not enough to make a difference.