I think the Chemist could be a lot of fun and the mixing sounds interesting if balanced correctly. Maybe it could use TP instead of MP though MP is just an arbitrary game mechanic, so they could still be “non-magical” and use MP as a resource to prevent them from having unlimited Heals.

One concern I have for a lot of people mentioning a healer that heals through damage is not that the damage aspect would be unbalanaced but that there are frequently situations where enemies/bosses become untargrtable while damage is still occurring. This would make it hard to have this healer keep people up during these mechanics unless they had enough other Heals that didn’t rely on damage to keep the party up. I know other games have done similar things before such as Warhammer AoR where there were battle healers, but they at least had the ability to heal if not attacking just not as well? I can’t remember their exact mechanics.