The recent W slow nerf is insignificant since he needs even less that 40% slow to catch you with his Q.
About the Q nerf, that's also insignificant. Riot keeps going for that idea of "if you stay in the inner circle you take 50% damage from Q" but actually there is **no reason** for you to do that because:
1. He will make up for that with an auto attack, so you will take 1 more bleed stack, overall **more** damage.
2. He will have more time for his cooldows and he will slow/grab you again.
So I thought about some options to give some actual counterplay to his Q:
(Not all together, just one would be fine)
1. Add recoil damage if you stay in the inner circle, something like "If a champion stands in the inner circle Darius gets hit back for 50% of the damage dealt".
2. Increase the cooldown on his Q if a champion stays in the inner circle. Similar to Gnar failing to catch his boomerang.
3. Remove the damage completely in the inner circle, for champions.