Simple fact of the matter is that if you ward like you should be doing you really don't have to worry about escaping as much as you seem to think. And in the situation when you do have to escape you should have your flash available.
Darius should also be building tank instead of AD with the exception of a Maw of Malmortius. This means that even when you do get ganked you should have enough health to be able to walk back to your turret. And while you are walking back to your turret you can be using his spin thing to stack bleeds on your opponents. Once you get near your turret you should be safe because of the turret damage and the bleed damage. In case they keep preasuring you, if you are building right, you fight them under the turret, hook them into you to keep them in the turret and laugh at them as you lop their skulls off. This is what I do most of the times when I get ganked.
As to people being too stupid to get away, you make it sound as if you can just walk away from him. 100% not the case. If you are up against a smart Darius you HAVE to burn your flash or die because he can just hook you in to keep stacking the bleeds before taking your head. This is why the ultimate got nerfed, because you NEED an escape mechanism to not die against anyone who has played Darius even a handful of times. And when you die to it, it resets so he has it next time you come to lane. Darius was one of the biggest pubstompers in the game.