There are items that not only heal you, but also teammates.
You can beat Death Ball by blocking. There's also skills that help give you an even more effective super block.
Basically anything a person has a problem with in this game can be beat by leveling, different skill builds, team-mate setups, or letting the CPU do stuff for you. The only thing that really annoys me is that CPU'S can spam recovery tech more than their meters should allow. But I can see where limiting them to player-style limits would make some of them WAY too easy, once you reach a certain level of play skill.
I'm surprised they let you heal in "Start with low health!" Style missions, too. Its overall quite forgiving, and a game that understands all level of players would like to play it.