Aplastante, Mirage doesn't take away the attack, Sonny 2's units' AI is designed to attack the unit with the least health (most of the time). Since Mirage gives your allied unit more health, thus will make the enemy least likely to attack them. If they do they take bonus damage by 400% (on the first level). This ability is scaled in favor of health for it's advantage because you gain 400$ more life, the healing is increased, and the enemy is least likely to attack that certain unit. However, DoT effects, will take longer to kill that target even though the damage is increased by 400$ the bonus life given to that unit will give it even MORE life than it have before (if scaled back down to the original). I have no idea for what reason that causes this.