Where's the love for Karthus?

Me personally, I love playing as Karthus, yet I find him to sometimes be a bit underwhelming. I would really like to see a buff or two on him, mainly what I had in mind was a 10% radius increase of Karthus Q (the attack itself not the cast range), but more importantly, I would like to really see Karthus Ult do True Damage as opposed to regular magic damage. While that may be a bit much I would even be willing to compensate by dropping the base power of the ult or extending it's cast time. I fell that these buffs should be implemented because karthus, while a great fun champion somewhat falls short of things that other champions have, such as a croud control options(stuns, snares, roots ect) and preforms very poorly against highly mobile champions, like Ahri, Syndra and Yasuo due to his Q's cast time and somewhat abysmal radius. True, the wall of pain can be used to slow enemies down and can work well in a team fight, in a 1 v 1 scenario a faster character can easily outplay you still. At best, the most he has is global damage which while it's great pressure, it sometimes falls short on damage, particularly early game when you are lacking build. His E is amazing though, don't touch that. What are your guy's opinions? I'd love to hear your feedback.

"Agony, ecstasy, peace. Every passing has a beauty all its own." ~Karthus