If you want to know how to beat Heroic Karazhan Julianne the Opera Wing then the video, deck list and notes in this post will take you through it and make it really easy for you.
By completing Julianne on normal mode you unlock the following cards:
To beat Julianne on Heroic one of the best decks is a Reno Paladin deck (full list below). As long as Romulo is on the board Julianne is invincible, so you need to take him out to deal damage to her.
Board control is important, being able to overwhelm her and keep sticky minions on board to keep the damage coming in each turn is the way to win as you will see in the video below.
How to Beat Heroic Karazhan Julianne the Opera Wing
Deck List for Heroic Karazhan Julianne the Opera Wing
Paladin Class Cards
Forbidden Healing
Selfless Hero
Equality
Shielded Minibot
Coghammer
Muster for Battle
Aldor Peacekeeper
Truesilver Champion
Consecration
Keeper of Uldaman
Ivory Knight
Lay on Hands
Ragnaros, Lightlord
Tirion Fordring
Neutral Cards
Doomsayer
Haunted Creeper
Huge Toad
Loot Hoarder
Twisted Worgen
Wild Pyromancer
Spawn of N’Zoth
Infested Tauren
Piloted Shredder
Polluted Hoarder
Sludge Belcher
Cairne Bloodhoof
Reno Jackson
Sylvanas Windrunner
Dr. Boom
Kel’Thuzad