Pros:
-Can burst a lot of damage early game/Continuously through out the game while having some defenses.

Cons: Not an extreme tank.

A lot of people seem to not realize that the outer area of his Decimate (Looks like a saw like shape when you highlight Decimate) Increases damage, So when you go to fight your enemy and pull him/her in, Use Crippling Strike but do not use Decimate right away, wait for them to take a few steps and use it. That should do a decent amount of burst.

Darius will not be good as an initiator even though his Apprehend is a really great spell to bring all the enemy team towards yours, you will bring them on top of you. Rather wait until a team either initiates or withers them down then use Apprehend.