Back to LoL after 2 month break, Karthus is still annoying as hell, but at least on EU servers people are way less skilled than they were two months ago. I'm usually playing as Ashe and rarely i can't get stats close to something like 15/7 or even less deaths - and if i have negative KD ratio i'm having a lot of assists ( stats from one of my latest games 7/7/30).
Brand as a champion is nothing special, his stun is easy to dodge, there are some better casters available. Rumble is interesting - but most players go berserk with him and feed too much. Most nocturne's that i've met were very skilled(one nearly took yi + nasus at lv 1 solo - they both left with 20-30hp)