No Errata
Q: If one of Ironskull’s Boyz is dealt 3 damage by an Attack action, is there a window where I can score Too Dumb to Die before my opponent plays a damage-dealing reaction during the successful Attack action to take my fighter out of action?
A: No.
Q: If one of Ironskull’s Boyz is dealt 2 damage by an Attack action and the attacking player plays a damage-dealing reaction to deal 1 damage, can I score Too Dumb to Die?
A: No. The damage dealt by the reaction is separate from the damage dealt by the Attack action.