Pretty much what Anonagon said. Darius is extremely strong in lane, but everything in his kit is highly telegraphed and has rather free counterplay.
Q has a very small radius that actually deals a lot of damage and stacks his passive.
W is a hefty slow with an aa reset
E is a long CD pull with a slow, doesn't stack passive. The passive portion basically means you should build health really quickly too, since armor is not as efficient vs Darius.
Ult has a 0.5 (I think) wind up before it triggers and only deals good damage if you have 5 stacks. Ult also gives a bleed stack.
Darius is arguably one of the strongest laners, but late game he is extremely prone to kiting and has a hard time fighting unless you have a strong primary engage champion.