Semi-gamebreaking bug with Karthus
Just played a game as Karthus in which I had 40% CDR and a fully stacked Ultimate Hunter. Ulted the enemy Rengar that died to my ult, and the enemy Fizz that died to Thresh, and the ult went on a full cooldown (2:40m) instead of the reduced CD (which was 1:21, like half).
Sure it's not an auto loss, but there's a big difference (1 minute and 20 seconds, to be exact) between having your ult earlier in late game teamfights. Not sure why but it happened unfortunately.