Unkillable monster due to pilfering bug

I have managed to make a 4300 divination card boss with pilfering scarab. Its IMPOSSIBLE to kill, it seems like there is some rounding error with the damage, i have a 100M dps build and i cant do ANY damage. I brought several uber boss carry with 150million dps, same, no damage. We cant even LEECH mana of it because we are doing ZERO damage. The map contained no mod related to the boss tankiness, only pilfering. There should be a hard cap to prevent invincibility

Same, can confirm it breaks at exactly 4000 cards. 20,000% toughness makes the boss invulnerable.