It really could be a more viable solo tree that can stand more strongly on its own merits without relying AS much with synergy combos (Ignoring that the game is all about Synergy combos)
It just needs to keep with the theme.
Right now what people dislike most about it is the fact that it doesn't synergize with the typical magics.
But doing damage as a percent of current health is an interesting dynamic, especially if that ability heals, since it will deal more damage when it's less useful for healing. I'm not sure if I like that or not, though, since it makes it kind of seem like the skill is being wasted a little no matter when you use it.
A skill that does more damage the more health you have? hmm... Or lets reverse that thinking.
A skill that deals more damage to the target the more you are healed by (to a maximum, because First Aid Broke yo) or overhealed by (preferably just healed by)
Why? Because it combos with Leech, Mosquito Swarm, Restoration, First Aid, Bless, and even the necromancy skill itself allowing it to combo with ALL skill types... AND it would be a skill both frontline and backline could use.
Turning your health into the enemy's bane.
As well because I suggested a damage cap, it doesn't need to be resisted.