Characters of that type would get a bonus for synergy but you don't need to focus it too hard.
To simplify it I'll ignore the initial 3 options itself and focus just on the roster. The numbers go into the top right, which you're trying to get as high as possible. When it's above 100% the round is over.
Each class type has a perk:
Assault get a 125% multiplier if they're picked first
Healers cap the number at 99%
Defenders bring back the highest TP person next round, if they finish it.
Basically the most generic line of play is start attacker for the bonus, then a healer so you get as close to 100 without going over, finish with a defender to guarantee the highest person comes back which makes it easier to go even higher next round.
100-149% is one person returning, 150-199% is two, 200%+ is three. The returning member is random unless a defender finished.
Now the three orders come into play more. If you pick Noah's, attackers get a bonus (+10), same for the rest. The bonuses are that quick flash of numbers after an attack so it's really hard to even see or break down everything, you get points for a lot of random stuff but it'll add on to the base number. The most important thing to know really is that a healer CANNOT finish a round. Even if you have 3 of them, and are at 99% already, they will all keep it there so you need an attacker, defender, or the hero character to finish. Hero characters don't abide by the same class roles either, a healer Hero won't stop at 99%.
I hope that didn't just make it even more complicated, lol. It's a lot of information overload but the core idea isn't that complicated, it just has a lot going on under the wrapper.