Had an easy time with all 3 heroic.
first guy: Druid with mill elements and general anti-aggro. The Spell Wish is amazing, since so many Druid spells counter his deck, from swipe, starfall, and Tree of life.
second: I used a Priest with lots of silences and some early/mid range minions. Thoughtstealing his 3mana, 6 armor/3cards spell is great. Inner fire is good, and so is divine spirit. He's also not the brightest cookie in the jar. I can see people having a bit of trouble with this guy, but a few tries and you'll beat him just fine.
third: Freeze mage! Doomsayers! 2x BGH! You just have to survive. Faceless is really good too, to copy his Obsidian Destroyers. Mirror Image is a life saver too. I think I even took 10dmg from one of the events and was fine.