Att vs Power. What is the difference for damage calculation?

When a skill says 280% damage to the target. Does that mean 280% of the card’s power or the Att?

Attack.

Power is just a combined metric of all the hero stats and the level of its special ability. It means very little to be honest.

I would think neither?

Attack is used in the damage calculation (attack vs target defense). I don’t think the attack/defence ratio is 1:1 so it would mean that 280% more attack is not equal to 280% more damage.

Exactly, a 280% special is an attack with 280% of the hero attack value.

How the damage is computed with armor and random coefficient I have no idea.