Have you done Expert Banquet of Angels today? That's a perfect example of mobs with high attack power and low HP/defense. Burning down one of them in a single round is quite easy. If you leave them all up, they HURT. Their overdrive is also very strong. You don't want to tank that, especially two at once.
Gawain (attack up + defense down) nearly doubled my damage. True story. And she's not even a legendary. Stacking the right buffs and debuffs yields immense synergy.3) It's true that healing is capped, but damage is also capped by money - unless you're willing to wallet warrior the shit out of this game, half your team is probably gonna be R/SR hime without ideal skills or the perfect element set and that's gonna put a FAR greater cap on your damage potential than your heroic soul choice.