Fun bosses this week. My strategies:
Razuvious (hard; also I found a bug): This guy's weapon is a huge problem, since his deck is loaded with them, so if you don't have a taunt up, you can take a surprise 20 damage. I turned the tables with a gimmick Priest deck having Mind Vision, Thoughtsteal, and Captain Greenskin, aiming to steal his weapon and kill him with it, plus enough defensive measures (taunts and oozes/corsairs) to not die immediately. I got amazing luck, so it worked first try. The bug is that a Greenskinned Runeblade only does 21 damage to face rather than the 22 = 11x2 that it should.
Gothik: Since his draw-a-card ability is auto-cast, obviously Blizzard wants you to mill him. I put together a gimmick Rogue milling deck having the usual Coldlight Oracle, Mukla, and Sap, but also Vanish and Kidnapper. Vanish did some serious work, but Kidnapper is fairly bad even in this deck. Somehow I win this with 1 health, his deck and hand both completely exhausted.
Rivendare: This guy is a cakewalk compared to the previous two. Shadow Word: Pain is great, Cabal Shadow Priest is great, Deathlord is great since he has no minions.