At the screenshot you can see that both units got negative casualities, this is with use my flamethrower mod and unsubstantiation faction mod, now as screenshots shows the tank got - 20% pentaly from faction. So it seems that a value for defense has no cap, at which point both of this units will heal on the attack. Not sure how that might look on attack values but just to keep that in mind and get some cap on them, since ther might be problems even on not moded game when ther is a significant technology gap between oponnents.
This is from beta version 1.2.3
