Rushoar – Reckless Destruction

I attacked a structure with a Pal that has the ability 〈【AUTO】 When this card attacks a structure〉. If that attack is blocked by an opponent's Pal, does the ability still activate?

Yes, it activates. An ability triggered by 〈When this card attacks a structure〉activates at the exact moment the card declares an attack on the structure, which occurs before the opponent designates a blocking Pal.