Can we do something for Karthus?

I get it that the next season is going to be about assassins, but Karthus has never been meta since I started playing this game in Season 4. I like the concept of the champion, but there's so many ways to avoid being killed by his ult and avoiding his damage completely. I'd even be willing to say that Karthus is the most difficult champion to play at a high level. Not to mention his ult is on like a 3 minute cooldown, and many champions have ways of avoiding it completely just within their kit, or they could simply buy . Karthus ult is also a 150 mana cost, which is extremely stupid. Most champions have their ult at 100-50 mana cost, or champions with a similar cost have their ult empowered and does more damage Kog'maw/Kassadin for example. Also, when he wasn't even meta he was nerfed around the start of the season again around the slow of his wall, when everybody was building .

Riot, you need to either significantly buff this champion, or schedule him for a rework. You cannot ignore this any longer.