I have defeated the lich king with all 9 classes. Here is the decklist so that you can do it as well! Hope this helps!
PS: Copy this: AAEBAf0EBIIOobcCmMQClscCDU1xigHJA6sE5gTtBLwI4xHrugLGwQLZwgLHxwIA
and then create a deck. It will ask you if you'd like to automatically build it. Happy hunting!

Custom Mage

Class: Mage

Format: Wild

2x (1) Kabal Lackey

2x (1) Mirror Image

2x (2) Doomsayer

1x (2) Primordial Glyph

2x (2) Shimmering Tempest

2x (2) Sorcerer's Apprentice

2x (3) Arcane Intellect

2x (3) Counterspell

2x (3) Flamewaker

2x (3) Ice Barrier

2x (3) Mana Bind

2x (4) Polymorph

2x (5) Nesting Roc

2x (6) Blizzard

1x (6) Meteor

1x (8) Kel'Thuzad

1x (8) Medivh, the Guardian

AAEBAf0EBIIOobcCmMQClscCDU1xigHJA6sE5gTtBLwI4xHrugLGwQLZwgLHxwIA

To use this deck, copy it to your clipboard and create a new deck in Hearthstone