Being part of a team is one thing; surviving as a team is another. To get the most out of the game, your team needs to establish a strategy right from the start.
Once you've chosen your characters, you must determine what role you're going to play on your team. Your role is determined by what powers you can use and reflects how you contribute to your team at the beginning of the game.
Here are the two suggested roles each character can play:
Protector: Uses powers that offer protection from damage (HP loss)
Tactician: Uses offensive powers that help the Warrior and their team
Mana Provider: Uses Mana powers to restore the team's AP
Power Mage: Uses powers that help the team gain special bonuses
Healer: Uses healing powers
Reviver: Uses the "Revive" power
If you have two Healers on your team, a good strategy would be to give one of them the Healer role and have them learn the "Heal" powers. Then make the other a Reviver and have them learn "Revive" as soon as possible.