MEIN GOTT, OP, why are you so pessimistic and denying everything we say. I respect how you and others have a different opinion, but most of us here write long articles in defense of the rogue DK and you just constantly repeat "too slow", "not that popular" or "bad against aggro". Do you think, that we aren't aware of this? Do you really think, that we defend the DK just because we remember the few victories she gives us, while we forget the losses?
No, tempo is not the only viable strategy in this game and rogue can also be a combo class. That's their real nature and the DK enables that. Yes, she's a bit expensive, but because she enables so much combos, this ability can easily outweigh her cost. Most of the cards in the rogue class are cheap for a reason - the class has the ability to play multiple cards in a single turn and many of them are really powerful and influential. Cards such as Preparation, Coldblood, Sap, Eviscerate, Vilespine slayer, Vanish (still relatively cheap in comparison to other AOEs from other classes) and imagine duplicating them. I could name more, but I won't disagree, that not every rogue card is that popular in this meta.
Do you know how I see the rogue class in the context of the combo arch-type? A one, which at one point stops interacting with the enemy board and starts executing its own win-condition. Right now this means the Mill strategy, before it kinda met making a gigantic Vancleef and stealth-ing him, maybe in the near future this can also mean burst (Maly, chargers with coldblood) or something else. It's just that Valeera gives you a whole turn (+ a card); she ensures you, that you will benefit from the HP. If you have some supportive cards, you can regain the board control and also stabilize. But if you don't - then don't blame the DK for not doing stuff she wasn't designed to. You see her as a 9 mana card and you expect her to win you the game just because you invested so much mana into her. Or to be the Saviour card in the bad MUs (aggro). But that's a narrowed way of thinking. Not every Dk should be played as easily as the warlock or the priest ones. Sometimes you really have to plan your future turns better and consider when would be the right time to transform yourself (see the warrior DK).
Yes, combo is weak against aggro. DUH. But saying, that the DK is weak against aggro and then insisting, that this weakness makes her bad in general, is the same as saying - why play aggro, if control decks have many ways to stop your aggression or why play control, if slower decks can out-value you etc etc? Of course you will see polarized MUs - some decks have their weaknesses and strengths, but don't let this hinder your way of evaluating cards or decks. Let me remind you of QR, which was only countered by the super aggressive decks, but which kept a whole arch-type in check (just like Jade dudu did in MSOG) and yet the deck was considered one of the weakest ones only by people, who blindly followed the statistics. Right now I want to give an example of Kingsbane rogue - yes, it's a dozen times more fair deck to play against, but the whole mill strategy (especially in wild) is really devastating for every slow deck. Not just control ones, but also other combo decks.
So believe what you want to believe. I will still insist, that the DK should definitely not be underestimated, as she holds great potential and with the time she will get better. The only thing I don't feel like arguing about, is the last sentence, as I can't foresee the future Rogue cards from the future HS year, but I think, that non of us can do it, so we shouldn't start with conclusions regarding the future of the DK before we see the next rotation.
Valeera for 9 manas give you one turn of survive, what is not a big deal because you spend your entire 9 manas turn playing the DK making 0 impact in the board, and need a least 4 turns of using the new hero power to get the value of Sprint, a 7 manas card.
Generating a specific card is a whole lot stronger than drawing a random card from your deck. While it would take 4 turns to equal the value of sprint, it doesn't take 4 turns to equal the strength of sprint's effect. If you are playing Valeera purely for the value aspect chances are you are playing it wrong, and that may explain why you think it is overcosted when it really is not. You need to play Valeera to her full potential to really see why she is an autoinclude in certain decks, and any card that is an auto include generally is not overcosted in my book.
Why Valeera DK Is So Insanely Overcosted?