Thanks for the feedback! Yeah, if we had more time, we'd definitely round up these rough edges, such as more feedback when the combo is performed and better telegraph for the enemies. As a countermeasure we made it so the player pretty much becomes invincible when charging, which reduces a lot of the frustration of not being able to telegraph the ranged attacks.
To answer your question, during planning we had some ideas for the combo reward, but self-heal ended up being by far the best option in terms of flow. I personally am a sucker for bounceback mechanics, and so loved the idea of coming from the edge of death to fully healed with a well performed combo.