How to fix Deathfire Touch on dots

Make Deathfire Touch apply on the first tick of damage only. It does not refresh after that unless a new source hits. This way it will act like every other single instance ability.

For persistent abilities like Anivia ult, Malz W, and Amumu W, have the first tick of damage apply the duration. After that standing in the spell will continue Deathfire touch. Leaving or getting out of range will IMMEDIATELY end it if the 1.5 second duration has run it's course. This way the duration does not continually refresh and it is up to the player to remove themselves if they wish for the damage to stop.