Guardians and Vanguards got taunts and extra defense, so sure they are harder to kill, but can be done.
Slinger, Shadow, Sent are easy prey to a skilled Scrapper, Commandos can be annoying but can be delt with as well.
Trick is to not blow your load all at once and be patient, waiting for defensive cds is the trick.
Aka cloaking screen, roll kiting, and saving cds.
It is a fact, a skilled Scapper/Concel can 1 vs 1 any class in the game, it takes skill and patience and even sometimes luck.
Come 2.6, the damage will be even better, and the tears will be delicious.