I had one game against a Darius and i was Shen.
Couldn't directly face him, but i could substain his poke attempts. I waited until he was oom, then asked for a gank.
I mean, he tried his best to all in me, but i always kept my dash in case, stayed defensive and substained myslef back up. I also got a kill and two assists with my first ultimate, so that was pretty neat. Either way, Darius couldn't hurt me enough to kill me, and when he's oom, he's only got his passive to help him(it's something, but not enough).
So basicaly, when i saw i was against Darius, i just said "meh", reached level six and ganked. If he pushed, i was sure to have my teleport to respond to him. Didn't lose my turret first.
When against Darius, RESPECT HIS GODDAMN DAMAGE. I had my shield to save me from his Q, and i just substained back the damage that got through. Not everyone play Shen, sure, but get this: Darius is a massive threat to ANYONE until he's oom or doesn't have enough to make his full skills. If he's only got enough to dunk, you can poke: if he wants to save his mana to ult, then he's gonna have to try to reach you without any stacks of bleed.
That's how i rolled with him. I also tried out the new black cleaver on Shen: the health and 20% cd sounded delicious, and the enemy team was rather tanky, so reducing their armor for our Caitlyn was essential. It's okay. Shen doesn't really benefit from it for his kit, though.