[WaifuApple]

For underworld flame being a burn AoE, see Salamander for that. Far more range to that, though that's likely a problem in itself. I don't think it just being a dark cinder inflicting ability is a good idea. It would feel out of place when tied to the fact that all other spells have an inflict (aside from Eternal Darkness). Not to mention that removing their access to burn demeans the burn hex even more. There should be a better solution than taking away the burn.

The bottom suggestion of yours for Essence Taking sounds like a suggestion for a new skill rather than anything to do with the name. Plus, I don't want to turn it specifically into a tool for PvP, rather than what it's obviously more catered towards.