As mentioned - you need a lot of investment to negate the RNG near the beginning (Plunderer enemies). One or more of the following conditions required for a stable clear: - Good RNG - Very high ATK - Skill Masteries - Modules
i brezze through the stage with my maxed out Executor without have to worry about skill timing at all, but leveling him to about lv30 should make it easy to clear the early part
For anyone wondering if you still can't do it at around lvl45-60 you can put the marksman facing right and just time your ops skills, once there are no enemies stop the skills if they have ammo and repeat once again