Holy. Freaking. Cow.
What an incredible upgrade. I don't think I'm being hyperbolic when I say that this is a game-changing card. Even more amazing, it is delivered into play as a part of the setup. If I were being pedantic, I would ask why his Claws are a starting element and not his Adamantium Skeleton, but I'm sure someone would "Actually" me with the fact that he had claws before the adamantium was grafted onto his bones.
In any event, this card is remarkably powerful.
Allowing you to pay for an attack event with your health is a huge benefit. This means you can effectively play two high-cost cards in a single turn, from the very beginning of the game. Only Star-Lord has a similar ability, but the cost for him is random and uncontrollable, since he is gathering encounter cards.
Wolverine, on the other hand, can plan for this expense by having allies to block or switching to alter-ego, where he can heal unlike any character ever.
The cherry on top here is that using the claws to play an attack ensures that the attack actually hits the enemy because the Claws add piercing to whatever attack you choose to use. There are several villains against whom this feature is incredibly effective.
If I'm being candid, I feel like this card drives home how ridiculous is it that Cyclops doesn't get to have his visor as a set-up ability. The Claws are a much more versatile tool and without his visor, Cyclops literally has to keep his eyes closed to not murder everyone around him.
Let me just say this about the claws: Wolverine already heals 2 points every turn, but he has an upgrade that takes him to 14 health. Not to mention, his 6 REC is the highest in the game so far. All of which means that spending health to play ATTACK cards causes Wolverine very little stress. If you toss in an Endurance and Down Time and Wolverine is almost unstoppable.