Yes good points about mercy stroke OP
I personally, as a war, use it as an off GCD free attack which helps with damage and doesn't take time since u can pop it between combos etc, also when I'm pacified post berserk use. I never use it for its healing effect, even when I'm fighting multiple weaker mobs at low health it's healing isn't something life saving or worth noting to be honest, especially since it obviously has a cool down period.
I personally would like to see it provide a self heal of the same ammount of damage dealt and shorten its cooldown period a bit