Kill and heal is also a really awesome skill, especially if you friend someone with a card that has a 2 counter. And 144 heals. It's great for lots of low or mid level mobs. But for bosses you want to consider slow hands and massive damage.
My understanding is this is a glitch / bug in the maths or programming / db storage used to calculate hp and attack rather than a player driven exploit.
Is it possible to grind for some evo cards? For example I need green armour. If I grind a green controlled area will the evo card eventually drop? Is the drop rate higher on last stage in area?