Hearthpwn

This is a pretty basic deck. It focuses on charge / rush minions with preferably divine shield and the outcast ability of the DH cards.

Illidari Felblade, Flamereaper, Eye Beam are mandatory. You also want at least 1 x Hulking Overfiend and  1 x Chaos Nova
You can change Frozen Shadoweaver, Dalaran Crusader, Spiteful Smith, Gyrocopter, Ancient Brewmaster, Raging Felscreamer and Nethrandamus for any divine shield rush / charge minion with at least  4 attack. Use "divine attack:4+" to filter in hearthstone, without "".

Mulligan:

Illidari Felblade
1 Chaos Nova
a 4 or 5 cost minion (keeping Nethrandamus is also ok, as long as it is the right most card. That way it won’t block the potential outcast activation)

What to do:

The first few turn we just hero power and attack the boss
On turn 3 play Vengeful Spirit

If you have Chaos Nova in your hand by turn 4:

turn 4 - don’t play a minion (Spectral Sight or Aldrachi Warblades would be the best cards)
turn 5 - play Chaos Nova
turn 6 - we start using minions to kill the 4/4 Shadowy Construct. Like the divine shield minions (with charge / rush) or Glaivebound Adept
turn 7 - now we try to keep control of the board. Focus on killing his minions first, then do hero damage

If you don't have Chaos Nova in your hand by turn 4:

turn 4 - Play a minion (preferably without rush), because next turn we will use Vengeful Spirit.
turn 5 - Play Vengeful Spirit and a minion with at least  5 health
turn 6 - we start using minions to kill the 4/4 Shadowy Construct. Like the divine shield minions (with charge / rush) or Glaivebound Adept
turn 7 - now we try to keep control of the board. Focus on killing his minions first, then do hero damage

Useful info:

Keep 1 Vengeful Spirit in case the boss uses Bonemare on a Shadowy Construct
Combine Ancient Brewmaster with Illidari Felblade or Glaivebound Adept
The boss has different cards that deal 1 damage to all enemie minions
If the boss steals a rush minion, especially Hulking Overfiend, you might need to restart
When you are about to die, you can use Nethrandamus to hopefully get a minion that will save u (like taunt or rush)

You can rewatch my fight here: https://hsreplay.net/replay/bDLZTK9trV9uZsLZgUdVC4