To everyone saying Karthus ult doesn't need change, most of you don't even play Karthus.
I'm not gonna get too into this because Riot simply doesn't seem to care about Karthus at all, but I just want to point out how funny it is that everyone who says Karthus' ult doesn't need to be change doesn't even play the champion nor has any clue on how to properly play him. If you don't know the subject material being talked about then clearly your opinion on the matter is flawed. If you main Lee Sin, chances are you don't know how Karthus plays. The same in reverse; if you main Karthus, chances are you aren't the best Lee Sin player. (That being a very general example mind you.)
When those of us who do play Karthus a lot are clearly banding together, agreeing that his ultimate is in a state where it needs to be changed, clearly we are the most likely to know what we're talking about. It's just common sense; the more you know on the subject, the more you're able to accurately identify what the problems are and what is a good way to fix it. And this goes both ways; there are tons of people who don't play Karthus as well who are suggestion tons of buff that are just absolutely ridiculous, unfair, or just downright broken.
The moral of the story here; unless you know what you're talking about, don't join in at the Adult's Table. Leave the Karthus discussions to the players who actually play Karthus. Sure, chime in if someone is spouting out a bunch of bullshit (everyone who wants to just make Karthus' ult unblockable, you know you're being ridiculous), but when someone is suggesting a slight buff that is good, don't call them out on it when you don't know what would be appropriate or not yourself.
Speak up when appropriate and be quiet when you should. To quote Illaoi, "We cannot comprehend the design. A raindrop cannot comprehend a river valley."