There is a card coming out very soon in Hearthstone that has some big potential called Elise Starseeker. She looks like this:
But the benefit to Elise Starseeker is not that you play her in a random deck and try to sift through all of your cards twice. No, she will appear in decks where you intend to go through the whole deck, don't mind having an extra card in the deck, and are just waiting till turn 20 to really get going. She will be a card you plan your entire deck and strategy around, not a throw-in.
So how would you do this? First off, you don't need any finishers in your deck at all when you are running Elise. You also don't have to worry about getting access to a bunch of gigantic idiots in the endgame because your endgame will inevitably feature a pile of terrifying yet random legendaries. When you arrive at that point not only will your deck be full of gas but any random card draw or filler you have left over in hand will instantly turn into monsters. Given that you can just run a deck with a low curve and endless removal, taunt, and board clears.
For example, in a Control Warrior deck you typically run a couple of win conditions like Grommash Hellscream and Ysera. However, you regularly have the issue that Grommash or Ysera is sitting in your opening hand restricting your choices in the early game. You can also end up with cards like Acolyte of Pain that are great card draw engines in the early going but which are worthless once your deck is empty. Converting that Acolyte of Pain into a Hogger is a big upgrade, because even though Hogger isn't great his swarm of gnolls requires a swift answer. Cruel Taskmaster and Fiery War Axe are similar in this regard and although they might find a use in the endgame they would be much better off as random huge idiots instead. Unlike Ysera or Grommash you can and should just throw down Elise on turn 4. She isn't superb by any stretch, but having the option to slam her down is *way* better than having a 9 drop you simply can't use. Most of the time you will have better things to do, but sometimes a random 3/5 that can fight a shredder and live is just fine.
That doesn't mean every control deck will run this of course. Some decks like Freeze Mage rely on specific high cost legendaries and don't want to run to fatigue. However, a deck that hopes to win by fatigue already can use Elise as a really strong win condition that isn't worthless in the midgame and which greatly strengthens the play against another control deck when both decks are almost out. She isn't going to be seen much, but it looks to me like she will fill a very powerful niche role that no other card currently occupies.
Elise looks to shore up two specific things - one, deck consistency in the early game against midrange and aggro, and two making the endgame against another control / fatigue deck a much better proposition. Knowing that your final few turns will feature an cavalcade of scary, unpredictable threats is a rough position for your opponent because they will have absolutely no idea what to keep to counter you. They can't think "Well, I just have to deal with Ysera..." because while you *might* have Ysera, you might have King Krush, or Feugen, or Confessor Paletress. Who knows! And when your opponent is down to only a few cards remaining it is a tall order for them to be able to deal with all the random you are going to pour out.
Both of those advantages are real, and I think they will cement Elise a place in the metagame. Plus control vs. control matches are going to have some absolutely stunning endgame situations that will make slogging through 20 minutes of trading minions totally worth it. The craziness that will ensue in some games with Elise will make this one of the best cards Blizzard has ever printed even if she doesn't actually see a lot of playtime. Low usage, big impact.