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The card is good in any class that can restore health, provided the spell pool is good enough to justify running it. Priest with Lyra worked because Priest has some pretty decent spells, plus you can chain activations with the obtained spells. Can't do so here, but is the spell pool higher quality?
The short answer is... maybe not? Losing the YotR sets means losing Ultimate Infestation, Spreading Plague, Spellstone, Branching Paths, and Living Mana. Naturalize is going to the Hall of Fame, which means you're mostly limited to bad ramp, summoning treants, board buffs, and what I'd call "miscellaneous functions" like drawing certain costed cards, drawing certain types like beasts, things of that sort.
A lot of the cards themselves aren't bad, the problem is their function. If you run this in a token deck, which seems like the most likely place given the spread of spells, it's going to suck when you pull Juicy Psychmelons, Stampeding Roars, and good ol' Savagery. Is it worth it to get multiple Savage Roars, the new 2 mana summon two 1/2 lifesteals, and Power of the Wilds?
Maybe. It's still a good card.
Mind Control Tech. It doesn't really a problem for ladder but a problem for arena and arena has standard cards only. I think it needs to be hof'ed.
and I don't agree with Preparation because almost all of the rogue spells are balanced around this card and if you hof it, those cards will be meaningless and you need to decrease their costs. So it seems not possible to hof Preparation . Maybe after this rotation if they start to create cards as not considering Preparation.
I think the reasons you stated are exactly why Preparation would be rotated. It's the most limiting card in the game in terms of design space (you can never print a great Rogue spell that costs more than 3, because it can be cheated out). Limiting one half of a class's entire kit is really bad. I'd expect it to get nerfed before rotated, but if they rotate then we can only hope that they'll at least adjust Rogue's basic cards to compensate.
But something needs to happen. A class shouldn't be designed around a single card for its entire life.
As mentioned, Rogues have had one of the best spells in the game since release, and as a result most of their spells are overcosted. Miracle Rogue is the reason cards like Leeroy Jenkins and Gadgetzan Auctioneer had to be nerfed. Quest Rogue is an archetype that was nerfed directly twice, and indirectly once with the nerf of Giggling Inventor (it was a strong card, yes, but it singlehandedly revived the archetype on top of that). Odd Rogue is a dominant deck, but due mainly to the 2/2 weapon, new neutral cards, and classic Rogue cards.
Odd Rogue is the only rogue deck that doesn't abuse Preparation, and that's because it can't. So every spell is balanced around it existing, and the day Prep gets rotated (I would bet money that it's next for the Hall of Fame) Rogue will be gutted.
GUYS! You're mistaken.
If you just discover one you STILL DRAW/Remove it from the deck.
Drakonid Operative discovers a copy, but does not state this.
Considering Molten Giant's text is technically incorrect (seeing as how healing shouldn't increase its cost if you interpret it literally), I assume it means "Cost 1 less for each missing health".
And in that case, it would work. But Blizzard is infamous for their inconsistency, so don't take my word for it.
If you aren't opening more Frozen Throne packs, you can dust Moorabi (Freeze Shaman is bad).
I wouldn't dust cards from the current expansion until you're sure you won't open a significant number of packs from it again, just in case you get the card again.
Explore Un'Goro as a one of might be worth keeping for Togwaggle stuff, but for the most part it's bad.
Keep Giggling Inventor. That card's really good right now, could end up being even better or not as good, but it's certainly not worth the risk.
I predict this change will be detrimental to elemental decks, especially Shaman with Servant of Kalimos.
Giants are strong in very specific decks with very specific synergies. Substantial discounts are necessary to make them worth it (or even play at all in arena).
Adding giants into the elemental pool will dilute the overall card quality for discovering elementals, since the giants will be unplayable in a deck not designed to capitalize on their discounts.
you could play an elemental deck and just not include giants if they dont fit your theme.
I bolded the important part since you missed it.
You can't avoid giants in the Servant of Kalimos discover pool. Molten Giant (in wild) and Mountain Giant don't work unless your decks are designed to make use of them, making them bad discovers. That being said, this is a fringe downside, and this change is for the most part a positive thing.
Wincon is Mind Blasts and Shadowreaper HPs, while delaying them from killing you pretty much. Turn 10, two Mind Blasts + three HPs is 16 damage, which is enough to kill someone post Alexstrazsa. Getting additional Mind Blasts with Shadow Visions can help solidify a win without Shadowreaper, or get you more Psychic Screams to keep them from playing things.
You could always run the version of this with that Priest legendary that shuffles their deck into yours and focus on more of a Fatigue game, I suppose. Or throw in a Velen instead of the Geist, since Skulking Geist isn't needed anymore. Point being, it's not really meant to be an OTK deck, just a good control deck that can control the board long enough to throw out a nice burst of damage at the end, with just enough reach to beat out most additional healing.
So the exploit doesn't work anymore, but the deck can still work.
I cut Hand of Protection and stuck in Emperor Thaurissan to buff the Stoneskin extra in one turn. Just make sure it has at least 18 health, then Humility it. Ideally, you can also buff one of the souls to extend the time you have to summon the horses.
Takes more luck, but still doable!