This changed my mind on several cards, so I greatly appreciate you taking the time to write this up!
For Thariel, do you know how the delve works? Do I get to choose 1 of 3 three sepaparte times? I agree it feels like the capstone of a midrange deck and reminds me a bit of Sage of Renewal. Not getting mana back slows him way down though.
Yawgmoth and Bryn were saying that they had to tone down Lysander's Justice from +2/+2 to +2/+1 because it was too oppressive in their testing. I'm not sure what to make of that, but we know Yawg has been testing chosen one for quite some time. Maybe he has a deck that can be competitive. Here's hoping. I do wish the Chosen One would glow or something to make it easier to identify. Sometimes it's in your hand and you don't know it before buffing. Maybe the glow would only happen if you have chosen one cards in your deck (since every deck has a chosen one but it usually doesn't matter).
I think Blade is the only one I'm unhappy with. It seems like a money trap. Drive pack sales and then nerf. I don't want to claim that was the intent, but it certainly gives that appearance. If a bunch of new gamestop players get rugged, it's going to be a net negative for the game by damaging it's rep. I just hope they have "THIS IS SUBJECT TO NERFS" written all over the place in flashing colors.
I'm fine with turbo coronet as long as the deck is <50% I think. If someone figures out how to make it competitive, meta will be the mother of all coin flips.
I think I can see Dearly Departed finding a home in deception. If nothing else, they can hide it for a turn or two. A hand crush deck might work. Cutthroat, double dealer, plus these could work. Pietro could hide one permanently. You mentioned Reflection.
Anyway, thanks again for the write up!
Thaeriel works like other delves, you choose 1 out of 3 cultists three times.
Back when chosen visions was still around, +2/+2 to the chosen one, chosen one was a rogue deck. Either you got a 10/10 frontline ward osiris and rolled some people or it got answered and you fell behind a ton. Some decks can handle it well, others like nature couldn't handle a big early frontline. So +2 health was a problem for some decks and you faced an immovable wall. Chosen one should get a glow but who knows what spaghetti code they have.
Blade is as good as or even better than Demo. You can't jam it in every deck. Some lists are too tight to squeeze in two 5-drops.
Hiding your DD on turn 5 is way too slow, just play CI instead. Maybe some weird magic transform deck with metamorph and reflect ele could work.