Headless Horseman should go up to the 3rd tier and have 2 branches in order to align with the other holiday lore spells. Especially considering the fact that you would need to get 685-720 spellements within the event period, compared to Krampus and Reindeer Knight that only need 190-225 within the same timeframe. Not to mention how if Headless got a spellement tree along with the other holiday lore spells, the layout would be as such.
I just posted a topic on how Headless is actually balanced, posted under "Ravenwood Commons", so if players would read that and be aware that Headless isn't actually overpowered could the upper branch be the damage increase?
Personally, I still want the Life mantle as the lower branch.