They felt auto-include Novice Engineer was bad in "most non-rush decks (and even some rush decks)". So why is auto-include Sylvanas in most _____ decks (and even some ____ decks) fine?
Honestly? Because she's Legendary and it's "okay" for super rare cards to have super rare-level power for decks. And due to the limited card pool at the moment, you're bound to have some auto-include cards just by virtue of limited options (seriously, most of the other 5 drops aren't that exciting for the most part). Shitty answer? Possibly. But, hey, rarity tends to mean this.
That's also why I was fine with Novice Engineer being so widely used: Sometimes there are just auto-include cards across all rarities. Honestly, NE was more nerfed not because of her being too good, per se, but more that the buffing minions made her really good. She was a popular buff target in general as well as deck thinning so board control / tempo decks got a lot of value from her beyond normal. As a 1/1, she's essentially just a deck thinner that dies to basically everything for free.
Works ok with Power Overwhelming, first trade up against a stronger minion with one of your weaker demons, then after you've traded, before it dies anyway at the end of turn, get the free 5 life. It's worth 2 1/2 cards in life anyway, so even if it has a negative trade value upfront, you can make up for it over the next two turns.
Extremely gimmicky, however, and you're using up valuable card space for this. And, besides, Power Overwhelming + minion to remove a creature is an inherent 2-for-1 against you (unless the minion was a token, I guess); granted, it's usually mana efficient here since it's a low drop + spell for a higher drop. Sacrificial Pact makes this a 3-for-1 and gain 5 life. Sure it buys you some Life Taps but that Sacrificial Pact could have just been a relevant card to begin with instead.
You can think up a cute trick for many cards but at the end of the day you just have to ask yourself: What am I cutting for this? What does it do better / different / worthwhile over that card in most situations?
Edit: But that's also from a super competitive "How do I win above all else?" angle.
I wonder if Mindgames uses the full 30 card deck for gathering targets, or only what remains undrawn. Also wonder what happens if someone makes a deck with no creatures and it's used against them.
It uses the deck as it currently stands so it can never pull what is in play / in hand / been killed already. And if there's no valid targets, you get this:
