@Meddler What would you guys buff if you WERE to buff Karthus?

Read the Gameplay thoughts post today about how you guys were at least monitoring Karthus as of right now, but theoretically, after data comes in after watching him post-exhaust nerf and he would need a buff, what do you think Karthus would get buffed in? His W seems like a decent candidate since it was nerfed a good while ago and I think a buff would put at least a little bit of power back into his kit.

Also, What are your thoughts on Karthus's differential gameplay between lanes? Mid lane he's forced to play a lot safer due to the assassin meta and the fact that he can get ganked from at least 2 different directions, whereas since Top lane has mostly Melee matchups and only 1 gank route so he can be more aggressive and maybe some people would say he's a bit oppressive at that sort of thing. I know he's not doing so good in JG right now, but you guys are already working on most AP junglers, so I'll wait till that clears up first before discussing that :P

Just thought I'd ask here since my comment during that post ended up getting buried at the bottom lol.