I think this is the best card of all the cards?
Hawkeye hits like a truck and is incredibly versatile, but "pays" for that flexibility with his 1 def and 9 hp. How can he hope to put out consistent damage when he can't take hits?
Mockingbird is the answer.
Hawkeye's other signatures are tightly synergized, once you have his board set up you won't have problems playing an arrow each turn. The basically leaves you free to put all your resources towards recouping and replaying Mockingbird every turn, then using her ability to block all damage from the villain.
It's bonkers. You prevent so much scheming because you're in constant hero form, you're hitting for solid damage and slinging an arrow every turn.
Even if you don't have the full engine setup and she's played more normally you can get her out, spend three to thwart 4 (which is fine value) then pay the cost to bounce her back to your hand to play her down again.
This card basically singlehandedly patches Hawkeyes glaring weakness. Play it. Love it. Never let her go to your discard.