Originally Posted by Izisery
So amumu's ultimate was changed, he had a bug where he rooted champs and they couldn't auto attack.
It wasn't a bug. It used to prevent autoattacks - stated in the description.
The bug with Darius is likely either (a) timing, or (b) an issue with whether his ultimate is classified as a gap closer.
(a) Currently, any two abilities that go off at the same time will both go off. Ezreal vs Blitzcrank is perhaps the most common... or Ezreal vs any CC.
(b) Snares only stop "movement" abilities. It's possible that Darius' ultimate isn't classified as a movement ability, like Bandage Toss and Zenith Blade (which can both be used during snares).