This deck let me beat Heroic Lord Slitherspear on my first attempt.
The goal is to survive until you can play Kel'Thuzad and Mirror Image together. The following turn, drop Sludge Belcher and/or Sen'jin Shieldmasta and I can basically guarantee that Slitherspear will give up on attacking you. Just to play it safe though, use Cone of Cold and Polymorph on the larger minions but do not kill them. If he has a full board, he will not be able to play larger minions to break through the taunts.
Playing Saboteur on turn 3 or 4 is highly recommended.