PLEASE UPVOTE IF THIS GUIDE HELPED YOU TO BEAT THE HEROIC PATCHWERK. THANKS! :)
How to win:
Destroy his weapon turn 1 with Acidic Swamp Ooze. This will stop him from attacking for one turn. Than use other cards to stop him from attacking by freezing him, destroying his weapon and using cheap taunts. It is very easy - check the comment section, most players manage to win in the first try :) Good lucky :)
Ice Lance use it to stop him for one turn - just freeze him - you don't want to deal dmg, unless fatal.
Mana Wyrm pump it up with cheap spells and attack - don't hasitate to make it a taunt minion.
Mirror Image use it to stop him for one turn.
Frostbolt use it to stop him for one turn.
Sorcerer's Apprentice makes your cheap spells free - don't hasitate to make it a taunt minion.
Arcane Intellect - draw cards.
Ice Barrier - use it to get one extra turn.
Water Elemental - freeze him and get extra turn.
Acidic Swamp Ooze - your best weapon against Patchwerk - destroy his weapon. TRY TO GET HIM IN OPENING HAND.
Mad Scientist - give him taunt and get free secret.
Nerubian Egg - Nerubian is your main damage dealer. Try to keep it alive.
Sunfury Protector - cheap taunt maker.
Coldlight Oracle - draw cards and deals damage cause Patchwerk does not have any cards. Even though he does not draw cards at the beggining of his turn he stills get the fatigue damage if you make him draw cards with Coldlight Oracle.
Deathlord - Patchwerk has no cards so no drawback, cheap taunt that gets you one turn.