Nothing too original but it seems to work quite well !
I'm not really high ranked (13 IIRC) but so far this deck provided me about 70% win rate so I think it might have some potential.
Deck list : http://imgur.com/lGUL7GE
Some basic explanations :
-Hobgoblins are here to buff mistress of pain or voidwalker. They can provide an amazing early game or use up some removal from your opponent. Hobgoblin followed by hobgoblin+walker/mistress is amazing.
-You have two demonfire and two demonheart which might seem a lot but you also have imp-losion to provide enough demon bodies. Most of the time those spells are like a removal except you have increased the attack value of a minion as a bonus.
-Felguard must be used with caution. You generally never want to play them early unless you're desperate or they are really trading very well. They start to be okay to use around turn 6.
-Jaraxxus will win you almost every end game versus control decks. Mal'Ganis pulled from a void caller or summoned on a board with some demons is a huge swing.
-If a mistress survives a turn you can usually buff her to abuse the healing synergy with life tap <3
-For your other problems in life you have the classic warlock removals (dark bomb, siphon soul, hellfire against aggro) and owls.
This deck is basically a few hours old so please share your thoughts on it !