We all know each hero has a special ability that can be activated during attacks. But how about when you're being attacked they can use their special ability too. Say when their health gets down to 1/4 remaining and their ability gets automatically activated.
Abilities give the heroes attacking advantages over the other heroes, which is what they are supposed to do. Also, the Queen already does lots of damage, summoning her special ability gives her the power to knock out very good tank units in a matter of seconds. Clash of Clans is meant to give the advantage to the offense, not the defense.