(If you take out the Doomsayers the deck gets half as expensive and a little weaker.)
The last few days I've been busy beating every single heroic boss using almost entirely this deck, and some mill rogue. I am not terribly good at beating bosses, but by using some basic AI loopholes and either this deck or a very similar one, most bosses become easy.
The last two expansions have brought two VERY powerful cards into the world that made such an overpowered deck possible, the first is Saboteur, this guy can practically skip the turns of many bosses completely. Pretty sweet. But the other card was brought by the very last expansion, The League of Explorers. This card is Animated Armor.
Animated Armor is easily the single most broken card for the current Adventures, I actually think that they will patch the AI of the bosses in the near future, because right now they DO NOT view this card as being anything other than a 4/4. Most bosses don't give a sh*t about a 4/4, they ignore it and go for face. Oh no. One damage. A swarm of 5/5s? Seven damage total. 20 damage otk weapon? A single point of damage.
So, this is how you win with this deck. First, you freeze the enemy minions until you can play Animated Armor. Then you heal and block until you get Kel'Thuzad and Target Dummy. For some reason once you have both Kel and Dummy out, the AI stops attacking completely. Then you just hit for face until you win.
Some bosses require slightly different cards, for example to beat Kel'Thuzad with this deck you just add a Majordomo Executus and some damage spells, or for Nefarian you add both Arch-Thief Rafaam and Alexstrasza, get him to 1 armor, use Alexstrasza to get him to 15 health and 1 armor, then use the buff from Arch-Thief Rafaam's lantern to make either of them have enough attack to one shot him, skipping his other stages.
All bosses have slightly different ways to beat them and I usually swapped out a card or 2 or 6, like getting some silences or eggs instead of Sorcerer's Apprentice. But most of the deck remains the same so it's pretty fast to swap them out. If you want to know how I beat any specific bosses just ask in the comments and I'll tell you everything I know!