The Tome Tampering combo might be a lot more powerful than you think. Being able to get 1 mana-cost version of cards can lead to certain disastrous results. The 3 cards above aren't actually a build-around, it's a package. You can put these three cards in any deck that wants a big discount. Maybe something like Cube Warlock or a Darkest Hour style deck where you just put a bunch of big stuff in your deck.

But by far IMO, the biggest abuser of this package is Mecha'Thun warlock.

I have explained the reasons why twice in this site but I'll elaborate again:

1. Cost reduction and card draw. Having 1 mana Hand of Gul'dan, Backfire, and Dreadlich Tamsin ensures that you will be drawing your entire deck with ease.

2. Mecha'tun Warlock has Runed Mithril Rod which further discounts the cards to 0 mana, essentially turning the deck into a miracle-type deck that starts their big turn very early (Around turn 5 and 6).

3. Having a 1 mana Mecha'thun removes the need to play Shadow Hunter Vol'jin thus reducing risk of your combo being...tampered with.

Another package worth mentioning is the Impending Catastrophe package. This card draws waaaaay too much cards. And having these cards at a discounted cost (by Runed Mithril Rod) makes it easier to yeet your deck away.