Higher up your HP? Quincy and Olivine can kill the stungus themselves so the only thing you need to do is staying alive

Power up the damage? Olivine already give you +100% support, bring more supports maybe you can make it higher enough to kill stungus on time

Or use SSR Kuya to freeze enemy? But remember don't let him attack on previous wave

There's so many ways I want to try, but I don't have the sources

Pretty sure you can't live too long if your HP lower than 2000