Hearthpwn

Hey there!

This fight is actually quite easy once you know what to do.

You want to mulligan for Archmage's Apprentice and possibly Mysterious Rune 

Survive playing and amassing as many cards as you can. Once turn 3 comes around, play the Mysterious Rune followed by one or two apprentices next turn. Pray to RNJesus for one of the secrets to be Duplicate.

Once duplicate is triggered and you get 2 extras apprentices, use them wisely. You want 2 out at a time and start spamming spells.

I played this adventure several times and every single time I got up to the 60 cards limit and 200+ armor.

I even milled him to death once for the lulz.

Hope this helped and good luck!