These new cards from Scholomance Academy were revealed today, including the Headmaster himself and several dual-class cards!
The iconic Headmaster Kel'Thuzad is bringing his power to all classes. Think of this effect similar to Firelands Portal or Apexis Blast but with a guaranteed result for complete removal. Any AOE or hard removal should be carefully considered with him. Cards like Shadow Word: Ruin or Plague of Wrath could be devastating in the right situations. One of the most powerful combinations currently might be with Shadowflame. With another minion on the board to target, you could ideally clear your opponent's board and get their minions and your own back. It will be interesting to see if there are enough board states that let you take advantage of Kel'Thuzad reliably. Otherwise as a 4/6, it's not doing much for you.
The new Rogue legendary Infiltrator Lillian has a lot of stats for 4 mana. It may seem underwhelming at first glance. But when you consider that its front half will likely be able to attack into something (akin to 1 charge of a Truesilver Champion) and then guarantees a second hit somewhere else, the 8 damage for 4 is pretty good. Not to mention, there are plenty of other cards to take advantage of the effect like Anka, the Buried and Necrium Apothecary.
Brittlebone Destroyer should be the new go-to for hard removal in both Priest and Warlock. The simplest combinations to be used with it are Warlock's hero power and Renew. Flik Skyshiv has been a must-include in every Rogue deck because even if it just removes one minion, it's targeted and not dependent on anything else. Though this does have a requirement, it doesn't seem to be asking much for a seriously powerful effect.