Just build him tanky cdr like before...he still brings MASSIVE damage from his dot which can be applied in AoE with his Q (which is pretty good damage too)...his ult is useful for executing, but what makes darius good is the fact that his high damage keeps you from ignoring him in a fight. Often, you don't get off more than one ult anyway because the other team is focusing you as it is. I think the change prevents cases where a big teamfight happens and Darius barely survives but can hold off one or two people because of the threat of his ult which is still up...He's still strong in teamfights, but he will have moments, like Mummy, where he isn't AS scary.