They can defeat Deathstroke?
Superboy alone is enough to beat Deathstroke. Bart can probably strip Deathstroke naked in less than 1 second. Deathstroke is also no match for Wonder Girl. Bunker can easily trap Deathstroke.
Deathstroke destroyed Bart's kneecap pre flashpoint and stood up to the Justice League repeatedly. I dont think it'll be that easy
Deathstroke has usually been an enemy for the first Robin more than anyone else, and it fit, since Deathstroke was more or less the evil Batman. Still, it doesn't debunk his potential as a fighter, and as other have said, he's been capable of standing up to some of the heavy hitters of the League.