@Gameplay Darius's R interaction with Presence of Mind wasn't fixed in patch 8.12
In patch 8.12 there has been a bug fix with presence of mind which was: "Many champions whose ultimate abilities use pet controls or multiple activations (ex. Talon recalling his R - Shadow Assault or Riven casting R2 - Wind Slash) now properly gain Presence of Mind's cooldown reduction on takedowns that occur while their ults are still active"
Darius was however not fixed.
Reproduction:
- Darius has a lvl 1 R without cooldown reduction = 120 cooldown
- Darius executes an enemy.
- After the 20 seconds passes Darius' R is at 100 cooldown, instead of the expected 120-20-12 = 88
ps: As said in the comments below his cooldown reduction also acts strangely, as it affects the recast time. Meaning after his recast time times out his R's cooldown reduction will drop less the more cooldown reduction you have for a maximum of 20 seconds at 0% cooldown reduction , and a minimum of only 9.35 seconds at 53.25% cooldown reduction (after taking ultimate hunter and cosmic insight)