Hearthpwn

Hello everyone, I am here to share a deck I use against Drakkisath with about 50% winrate. Disclaimer: this deck is not the exact version of the deck that I use as I don't have all of the legendaries nor do I expect you to have them all, though I have all of the cards that make this deck "work". Having done some theorycrafting though, I am certain that the listed deck is the best possible to face one of the hardest heroic bosses Blizzard has ever introduced. I will list some of the alternative card choices below.

The matchup.

Drakkisath should almost always win boardcontrol with double your mana (at least before the Old Gods expansion changed that with Y'Shaarj, Rage Unbound) - the idea is to stall as long as possible and pick the opportune moment to use Lightbomb and finally win through fatigue.

Though Drakkisath's Command and Twisting Nether are very annoying, the real problem is his card Kidnapper, which basically negates your previous turn while playing a 5-3 for only half his mana. That's a huge tempo swing. This is the reason I've designed the deck to have as much as reach as possible - half of your cards do something immediately the turn they are played. More importantly, your big minions will almost always be able to survive trading - an important criteria, when you only have half Drakkisath's mana.

Know your enemy.

Drakkisath runs the following cards:

1. Drakkisath's Command - try to bait these out. Best target is Sludge Belcher (or Troggzor the Earthinator if you steal it), but I have seen it used even on a Big Game Hunter. You have Mind Control. Stop complaining.
2. Twisting Nether - game is hard. Try to anticipate and protect yourself against it. Play Dr. Boom or Onyxia on the first turn to bait it out. If he has one minion on the board and you have a taunt + one other minion, he will still use it. Deathrattles help a lot (Cairne Bloodhoof or Sneed's Old Shredder), yet those cards can't kill Boulderfist Ogre with one hit. You should probably still run at least one of those just to counter his boardclear.
3. Kidnapper - the card that will lose you the game. You think your Sludge Belcher is going to save you? Think again. So you used Mind Control on his Force-Tank MAX? How unfortunate if someone were to return it to your hand... On a serious note, this is why you want your minions to do something immediately the turn they are played. Best targets to be returned to your hand: Big Game Hunter, The Black Knight, Dr. Boom, Icehowl, Frost Elemental if you don't have all of the legendaries and choose to run it, Ragnaros the Firelord that has already killed a big minion, the summon spawned by Hungry Dragon or Onyxia,  Onyxia itself, maybe even your big ass Deathwing. Imagine Deathwing returned to your hand - twice. Oh well, a man can dream.
4. Flamestrike - not your biggest problem. Usually it will only kill a minion that has already done its job, though you should watch out for it when you have a single Slime separating you from defeat. Keep in mind that if you damage your Kel'Thuzad with trades, it will leave it vulnerable to Flamestrike.
5. Force-Tank MAX - Ideally you would use your Mind Control on it - it's the best card to steal - but Big Game Hunter will also do the job. Beware: if you plan to Lightbomb next turn, Drakkisath playing a Force-Tank MAX might throw you off.
6. War Golem - the third best target for your Big Game Hunter.
7. Core Hound - the second best target for your Big Game Hunter.
8. The Beast - I've got The Beast in my sights.
9. Boulderfist Ogre - just as annoying as Force-Tank MAX. Ways to deal with it: kill it with your big minions, target it with Vol'jin, damage it and use Lightbomb or try to steal it with the Sylvanas Windrunner + Lightbomb combo.
10. Drakonid Crusher - vulnerable to Lightbomb. The upgraded form is a viable target for your BGH, but you should try to keep your health above 15.
11. Lord of the Arena - kill it with The Black Knight.
12. Ogre Ninja - a sneaky bastard. Can get through your taunts, so beware.
13. Hungry Dragon - card that might win you the game. With confident flourish, the glorious A.I. will use Kidnapper to return those pesky one drops to your hand. Most spawned minions: Pit Snake, Angry Chicken.
14. Sprint - Drakkisath doesn't like running out of cards.
15. Mindgames - the reason to run low value minions that have a battlecry. The more you have 10 mana legendaries in your deck, the more Mindgames will punish this. If you are lucky, Mindgames will spawn a Faceless Manipulator, Big Game Hunter, Frost Elemental, The Black Knight or Vol'jin. There is also a chance it will summon one of your taunts, giving more targets for The Black Knight.
16. Troggzor the Earthinator - card that might cause you issues. Will spawn a Burly Rockjaw Trogg if you are forced to use Lightbomb. Otherwise just trade with your minions or use Mind Control if you have the board and the means to easily kill the summoned 3-5.

 Reasoning behind the cards.

Shadow Word: Death - There might come a situation where Drakkisath has the board under lock and key and you seem to be out of easy answers. This card will delay the inevitable while you pray for your Lightbomb or Deathwing. It has an immediate effect, yet it will lose you tempo as it trades 1 for 1. Therefore I run only one of these to be used when all hope is gone.

Vol'jin - the unsung hero of the deck. It has an immediate effect and great synergy with rest of your cards. It will allow your smaller minions (Big Game Hunter, Sludge Belcher, Whelp, The Black Knight, Boom Bot) to kill the target or leave it vulnerable to Baron Geddon and/or Lightbomb. Furthermore, if used on an upgraded Drakonid Crusher, Boulderfist Ogre or War Golem, your trusty troll will survive Lightbomb the next turn. Drakkisath's card Mindgames is also a very good reason to run this low hp minion.

Alternative card choices.

1. Holy Fire
2. Frost Elemental
3. Cairne Bloodhoof
4. Foe Reaper 4000
5. Sunwalker
6. Soggoth the Slitherer
7. Maexxna