I’ve noticed that both Mend and Rejuvenation traits don’t work consistently with the Overheal perk. In the same battle, both traits may activate correctly for one creature, but the next creature will have only one of the two traits activate, and the next will have neither trait activate. All the creatures had 100% current health at the time.
There is no way to predict which creature will have the benefit of either traits on its turn during a battle. Both traits do activate when the creature has less than 100% current health. The problem only occurs if the creature is fully healthy at the start of its turn.
Device: Apple iPad Air 1
Operating System: iOS 10.3.3
Game Version: 2.4.5 (although the in-game title screen incorrectly shows 2.4.4)