It's pretty shitty to give what Morellonomicon does for free. And yes, I do get that ignite isn't multi-target, and I do get that it has DoT, I get the differences. But Grievous Wounds is, you know, pretty strong given the extent of lane bullies in the meta.
For example, I'm really tired of playing Mundo for instance, and then suddenly, the pride and joy of almost any champion (level 6) is cut short, because it takes just a point and click spell to render my ult fairly useless, while with Morellonomicon they'd have to reduce my HP to under 40%. And that requires magic damage, and that is an item, which costs money and time to build. I can't exactly counterplay a summoner spell like Ignite as Mundo.
Ultimately, just give people at least a glimmer of hope when facing lane bullies who take Ignite. It's just too god damn strong with how many people are playing early game lane bullies (Darius for instance, with his insane DoT early), and I doubt it's going to change.