Cards that combo well with this include:
-Dust: her ATK can affect every minion in play
-Thor: his ATK can affect every minion engaged with a player
-Tigra: additional ATK can help her defeat a minion to get her heal
-Beta Ray Bill: additional ATK can help him defeat a minion to get his thwart
-Magneto (campaign ally): additional ATK can help him defeat a minion to get his heal
-Lady Spider: her THW can affect two schemes
I love the concept but I think this card is overcosted by 1...
3 Effective Resources (ER) for 5 damage under condition is not good. And obviously, 2 damage is terrible.
I think 1 ER roghly equal to 2 damage so 2 ER would still be bad for 2 damage but would reward you for taking care of the main scheme by giving you a bit more value than usual but with a condition.
Time changes all things; and in the case of Hard Knocks it is Wolverine who has brought the winds of change to this card. While indeed cards like Tackle are more powerful overall; that has a pre-requisite required to unlock the damage in addition to the stun. If Wolverine plays that card using Wolverine's Claws he will only deal the stun; and while a stun for three hit points and a card is not the worst deal in the world, it's also not really good enough to include in most decks. So, instead let us look at Hard Knocks through the lens of the Captain Canada.
When used in a Protection aspect deck; Hard Knocks provides a way to utilise Wolverine's Claws defensively; as their activation is a Hero Action for an Attack Event you cannot funnel many of Protection's best defensive cards through it. Hard Knocks offers a way by allowing you to spend one card from hand (the Hard Knocks), exhaust the claws, lose three hit points and gain a Tough status card by defeating a minion with 4 or less health even if that minion has tough (because Wolverine's Claws gives this attack piercing). That's a huge deal for any Protection Wolverine in solo and it is also very relevant in multiplayer as you can both deal with a threat attacking one of your team mates plus take an attack without losing more any more hit points outside of the three already spent. Wolverine might have inbuilt healing, but Tough gives that Healing Factor regeneration a bit of time to recover from low health.
When we are not just leaning into Jimmy's decks Hard Knocks has a lower ceiling, but the floor for this card is huge in any hero who has great on board resource generation, ways of boosting its damage like Gambit or loves to have toughness like Colossus. Protection Thor is another place where this card has a great home because of Thor's preference for fighting minions with "Have at thee!". In the opposite style Drax likes this card also because he can use the tough status to gain vengeance counters without losing hit points. Last of all heroes with triple resource cards like Captain Marvel and Hulk are able to play this card for a net two cards instead of three or four.
Some other card to card synergies in Protection include Bait and Switch which will let you turn that toughness card into four damage right the villain's keister; Unflappable which will be triggered when you take no damage (thanks to tough) and classic Protection upgrades like Electrostatic Armor
All of this makes Hard Knocks a staple that you should pull out when you are starting to build a Protection deck and you should always seriously consider keeping it in the final build, cutting it only when it is clear that the deck is not needing an injection in the minion punching direction.
The Best Defense… is a good offense indeed.
At baseline, this is 4 thwart + 6 damage for 4 ER which is great. However the kicker is he needs to get charged up by you getting attacked so you need to mitigate 3 attacks without Stuns. Since Justice isn't the best at doing that, it means your character kit or Allies have to do the majority of the heavy lifting. This puts him at his best when playing Colossus as he's built to take hits to the face.
The two requirements for a deck that wants this card are:
You have to be able to go to Alter-Ego often. Since the card is limited to an Alter-Ego action and it isn't a high impact card that you would flip to Alter-Ego just to play it, then you have to have a deck that can flip to Alter-Ego relatively easily (that is with low risk of getting schemed out). Otherwise you just won't be able to play it.
You have identity-specific cards that you would play over any other card in your deck most of the time. If the card you're shuffling back isn't better or enables you to do something that most of the other cards in your deck can't, then it's not worth reducing the chance of drawing the cards you would rather play. Generally Upgrades/Support are what you want to prioritize playing to buff your character and the cards you're shuffling back are not those things most of the time. So doing this is only worth it after you've set-up the rest of your Upgrades/Support.
What I found when playing this card is that it's not worth it to play it without X-Mansion on the field as you're spending a card without affecting your current situation at all and there are not many situations where you're not better off just spending the card as a resource. With X-Mansion in play, the cantrip makes up for the inherent weakness of the card, however the timing can be awkward if you didn't start the turn in Alter-Ego.
Ideally you want to sequence any card draw at the start of the turn to have the most information for which cards to play vs use as a resource and it makes this card awkward to use when you start in Hero form because the majority of the cards in most decks require Hero form so flipping to Alter-Ego usually happens at the end where the cantrip is irrelevant most of the time because there's a higher chance of drawing into something you can't play.
So overall the card is awkward to play due to needing multiple things to line up for it to be worthwhile. You would probably be better off considering other options.