Like miladesn said, the best combo with Don seems to be something with charge, so Argent Horserider stands out the most. 10 mana for a 5/6 and a 7/6 divine shield charge.
In theory his battlecry is incredibly strong. Blessing of kings is +4/+4 for 4 by itself, but the strength of a card like that is it is almost always effectively 'charge' since its immediate impact will hit a minion either trading or going face, which then ideally forces the opponent to use removal which continues to give inititive to whoever used the buff. These Goon cards are all opposite in being rather slow and clunky with value coming later. Don might be way too slow to work, but you might be able to pull off some sort of bullshit.
I switch C and D tier.
And I have a tier in between A and B tier because in that list there's a massive gap between A and B.
Like say Thing from Below is tier A (top tier as hell card) and Young Priestess is tier B (better than basic card, playable in a competitive deck)... there's a massive gulf between those two cards.
So I have S, A, B, C, D.
S: Top tier cards, you put this card in your decks because it's too good not to. Tirion, Fandral, Thing from Below etc. These are usually the cards that the community or Blizzard looks to be on the nerf list because they are such brain dead auto include.
A: Strong cards, good enough to be used in competitive decks but usually meta dependent. Baron Geddon, Ysera etc.
B: Good cards but usually not broken enough to be included in most competitive decks. Stuff like Seal of Champions, Mulch, Flame Juggler.
C: Good enough for Arena tier. Very pickable cards in Arena because they are usually decently stated above basic cards. Stuff like Aberrant Berserker, Evil Heckler, Kvaldir Raider etc. But they are a bit too basic for constructed play.
D: Genuinely bad/terrible card that I would not even pick in Arena. Stuff like the 6 mana 5/5 that draws if it attacks and kills a minion. Also Purify.
So far in this expansion only the Priest cards are S tier for me. Like the 5 mana 5/6, 3 mana 3/4, Dragon Potion and 1 mana steal 2 mana minion.
The hardest part of evaluating a card to me is sometimes less about the card itself and if it's viable to build around.
Most obvious example for this in HS would be Mysterious Challenger. Like, that card is busted--it can draw and play up to 5 cards from your deck. Thins it out, has a strong statline despite that, etc. It was meta defining due to the degenerate curving, where plopping him down with board advantage was straight up checkmate in certain matchups.
But post-rotation the card still exists and basically vanished, what does that mean for the card? Is Challenger S or A tier? Without the curve it loses out on so much power that it just doesn't quite work...but the card is still ridiculous.
The couple to this is Menagerie Warden. That effect with that statline I still say is just busted. But the deck didn't break out quite like a lot of people expected...does that mean Warden was overrated and isn't that good, or the rest of the deck just still isn't quite there, but eventually could be and that card is the next defining meta staple?
That to me is why it's so hard to look at some of these. I'd say a good amount are pretty standard at looking at, like it's really obvious when you see a good for arena but will never be constructed good card. But there can be times where a really strong card actually just doesn't really pan out, and I don't know if that means the card was actually not strong or not.
Maybe that 3/5 windfury is playable. If you buff it up enough it could be very difficult to deal with and also capable of finishing the game on it's own. I like the buff hand theme because it makes you revisit your thoughts on a lot of old cards, since minion's scale at different rates. +5/+5 is not equal to all minions.
Yeah, the buff working well with other minions you don't see is actually one of the more exciting parts of it.
We may very well see a day where we put Angry Chicken willingly into our decks.