how about equipment? Properly geared units are much harder to kill along with team composition and synergy. i.e a team of units with adrenaline rush has the possibility to keep chaining attacks and build up combo bonus. One of the three star supports give a shield that blocks a set amount of damage and if you can combo her with that 2* warrior with aoe taunt it will make things easier, although granted you probably need to evolve her first.