Just revert all of the Darius changes from his release and only give him the following changes
- Higher base damage on Decimate (40/70/100/130/160 from 20/40/60/80/100)
- W now refunds mana cost and half cooldown on unit kill.
- E slows for 65% (instead of 90% from release and 40% from live)
There. He's fine.