Scheherazade is the last agent you're able to recruit. Perhaps just as well, since once you put her on squad, it's very hard to justify removing her. Her swinging blades are deadly against mobs and bosses alike, her distance attacks are reasonable, and her teleport sword gives her both battlefield control and an infallible answer to those annoying snipe troopers which infest the later levels. She's not technically a shieldbreaker, but her damage output is so high it hardly makes a difference. Note also that boombots don't explode when melee attacked, making them yet another source of fodder for her sword.
Her only weakness is that chained attacks can sometimes leave her vulnerable to damage from other sources, staggering her so that she can't switch out in time to avoid death. So while it's tempting to have her just berserker barrage every shocktrooper you come across, be sure check your health and shields before diving into the fray.