During tower defense levels, position your tank and their two minions correctly. They minions and the hero will not do that much damage, however they can soak up damage while holding enemies back. This allows other heroes to take them out. Place them at choke points that lead to your other heroes. In RPG combat levels, fill the five slots for your party with a balanced group. Fill them with one of each type of hero (tank, marksman, mage, support, and cannon).