Refresh flash CD if killed during Darius ult
I am sure this happens to many. You want to dodge Darius ult, but you flash just a little too late.
So despite not being in range of Darius ult anymore, you still die from it. Flash gets on cooldown. You wasted it.
There are many possible solutions: if you flash it, could means you dodged it (would be a nerf to Darius). if you flash but die, refresh flash CDR (as you refresh Cait ult cooldown if someone dodge it). Since you're already dead, don't make flash proc (I understand flashing Cait ult is just being dumb, but flashing Darius ult is another story).
I don't know what you could do, but as it is, it feels frustrating to waste flash. It also feels weird to be miles away and still being hit by Darius axe.