Does the tower deal any damage? What would be cool is if the amount of damage dealt by the tower is heals the player in some ratio.
Maybe make this only work if health is less than 100%? Otherwise unlimited healing is a bit crazy to contemplate. Even then, this tower would be super useful. A neat idea, but maybe better for a unique tower so it can't just be swapped in whenever healing is needed. With my changes, it could be stronger healing, something like 1% + 1% per 14 levels. I like 0% + 1% per 14 levels so it caps at 7% per round at 98/99. 7 being associated with light in some mythologies.
Agreed, healing should be limited. Maybe can heal up to 1% per tower level? So a level 99 Druid can heal up to 100%. And as jhoijhoi the healing per round could be tied to how much damage the Druid caused that round. This way it would take some invest to get notable results. Then it wouldn't necessarily be unique and become a rare tower maybe?