So much time spent on just getting a card back, but whatever. Beating all the heroic bosses was its own reward.
Sapphiron was ridiculous. The only heroic boss where I really had to give in and netdeck.
I used this deck:http://www.hearthpwn.com/decks/93542-budget-mage-for-heroic-sapphiron
I was down a Blizzard, and used a Counterspell in its place. Counterspell is quite good here. Either it blocks the 8-damage to the face spell, effectively acting as a third Ice Barrier, or it nullifies a freezing spell, letting an extra Thaddius get a shot off.
Against Kel'thuzad I used a control Paladin, like Titandrake, but maybe not. I added Kel'thuzad in there, which allowed me to have a huge board presence to take him down way before fatigue started. A Guardian of Kings saved me at some point.