Karthus spell range

So recently I've picked up playing Karthus. I've tried him out before hes a fun champ and amazingly strong, but I've realized that he has one major draw back. He's a good mid lane mage and has the potential to do so much more for engages but most mid lane mages out range him greatly. Unloess your in lane against a melee champ like talon most of them will zone him with heavy ranged pokes keeping him at bay and keeping him from farming. It's such a waste for him to have such potential and not be able to use it.