Obviously a very good card for Drax and his huge attack. But I was surprised to see how useful it is in a Spider Woman deck. It allows her to deal two attacks in a row, plus triggerring "superhuman agility", and it makes a great combo with "skilled strike". And if you were in AE at the start of the turn, you can see how many boost icons you're gonna get.
Hero Interrupt: When your hero makes a basic attack, discard the top card of the encounter deck → reduce your hero's ATK for that attack by the number of printed boost icons on that card. If that attack still deals damage, ready your hero.
Leading Blow is better than Skilled Strike for any high-ATK hero, because you have the option to split the damage across two different targets. Thor, Hulk, She-Hulk, Drax and Spider-Woman are all potential users for this card and since Skilled Strike gets quite a lot of use you'd expect this card to do the same. The random damage is obviously a downside, but my feeling is that not facing a three-boost card in my own turn is compensation for only getting one damage out of Leading Blow so the card is well worth it at ATK 4, let alone anything higher. Drax has really opened up the space for aggressive decks in the Protection aspect.