Standing still
The number-one run-ender is treating Holocure like a standing shooter. You are not. The wide circle is your only reliable defence, and without it the swarm will wall you. Mini-bosses spawn every 2 minutes and bosses every 10, so the circle never stops mattering.
Wasting the Special
The Special is panic insurance, not a damage button. Spend it when a pattern is about to delete you, not to clear chip damage. A character with a screen-clear Special (worth more than a passive boost) is the one to learn first.
Overlap builds
Taking two weapons that hit the same angle leaves the other angles exposed. Cover the gap instead — a melee weapon for swarms plus a ranged weapon for chasers answers every direction. See weapon synergy for how collabs free a slot.
Fixing the habit
Before each push, ask: am I moving, or am I standing? If you are standing, you are already in a bullet.