What if Deathfire Touch's damage ramped up?

To prevent abuse with DoTs, something like a debuff that stacks every time the target burns for 4 seconds.

First application? Decent damage. Second application? Better damage. Third application? Starting to get scary. And so on and so forth.

Part of the issue with Thunderlord's vs Deathfire is that given Thunderlord's cooldown, if you stick around long enough to proc it a second time, the damage isn't that different from what you'll get from a full 20 seconds of burn. And that's just silly. If Thunderlord's got nerfed back to 30 seconds then this wouldn't be an issue, but I'm not sure if Riot wants to do that.