Many people have already stated a lot of what's needed. My opinion on a few others:
Frozn: a 2 star with -3 life min 8. Gives them a solid 2 star, an a viable turn 1 card that's not hosing the bonus of good cards.
Sentinel: a 2 star that isn't so SoA vulnerable or SoA foil. Something like 7/3. Copy opp dmg? Copy Bonus?
Freaks: a preposterously powerful 4 star that can be banned in place of Bogdan.
Frozn are to young to make such comments. They only have 20 cards. I do see the need for more cards that don't need their bonus. Turn 1 cards aren't plentiful enough in their current line up.
The Sentinel problem is last time they got a good 2* it was too good. A good 2* is needed but not so good it gets banned again.
Freaks have a great 4* line up. Bogdan then grudj Wolfgang and now Madelone. Madelone is great a 4 pill lead will net you poison or put your opponent in a poor pill opposition. Which with Freaks raw power could spell the end. I'm going with and Olga replacement more than a Bogdan replacement.
Stompah or Kalindra (outside of elo)? They're better with bonus, but still pretty dam good without it.
7/3 2* would be pushing the cap with the noticeable damage output. Therefore, it would most likely wind up Backalshed.
And Bogdan is the preposterously powerful 4 star.
Ok, make the Frozn 7/2 then, it's the ability that's important. They just need a better option for turn 1 that's not a throw away, or wasting their win cards.
Freaks have been gutted. It was bad enough when members of the circus trinity were banned. The consequence of Olga's perma ban is a defacto perma ban for Bogdan as well. Mono Freaks are strong with Bogdan, and they are pretty bad without him. Madelone is a great sub for Grudj, but is not comparable to Bogdan.