the issue is you still get hit by sucker punch
0 Atk Black Glasses Darkrai Sucker Punch vs. 0 HP / 0 Def Dragapult: 210-248 (66.2 - 78.2%) -- guaranteed 2HKO
you have to keep dragapult healthy and not at sucker punch level incase he has it, which will be hard if you arent running hdb, which...