Blood knight I may tech in if I start seeing Paladin, but where I'm at (15-10 up and down) there aren't any. Mostly I'm facing zoo with the occasional Rogue or C'Thun deck.
Shifter I didn't pull and isn't a crafting priority for me--it's a fun card, for sure, and if I had it I'd tech it in to see what I could do.
Varian I dislike in the style of CW I like to play because I rely so much on my battlecries. If I lose the Justicar battlecry, for example, and I'm also trying Malkorok out, which so far has been better than just running an Arcanite Reaper in that spot. Puts something on board and even a bad weapon is pretty decent for reach or to give me a ping. Only got Cursed Blade once and it was a non-issue.
Blood Brothers is a fun one of--card advantage really helps the control game, anytime you can get it without getting closer to fatigue I think is very powerful. I even run Blood Brothers in my C'thun Warrior:
I don't like C'thun itself, but the synergy cards are very strong. Bran+Ancient Shieldbearer is 20 armor. Bran+Twin Emperor is three big taunts. People also prioritize removing Bran which means an Ancient or an Emperor can stick and then I can dupe it with Blood Brothers for another 10 armor or big Taunt.