Bane of Doom
I have been perfecting a Demon deck that is playable for about 23 levels of warlock and i have to say its nearly impossible to *successfully* run demons for some simple reasons.
1) You're killing your own cards essentially helping your opponent with free removals
2) Sure these demons cost less, but removals are plentiful so you lose twice unless your lead is commanding.
3) Demon synergy is non-existent apart from a 2/2 buff.
Things you'll absolutely need to take into account for varying degrees of success:
1)Think like a Priest: Card efficiency is #1 priority. Buff the minions with battle cry cards and make sure they have a chance to trade up, or you've already lost. This means waiting to synergize even though you could play the demon early.
2) Avoid playing Felgaurds until mid game (unless youre running a very low-cost deck): Yes, they cost very little, but you screw yourself if you coin it on turn 2, or play on turn 3. Chances are, the opponent is going to trade up on you.
3) To run Flame imp, Pitlord and your draw you need some heals: +4 health priest, +3 health farseer, +2 health voodoo is a good curve and one of each is easy enough to include. Farseer and Voodoo add to card efficiency and are versatile.
What i think needs tweaking:
-Succubus should remove a card from the top of your deck. Should be 3/4.
-Infernals should have a 2 dmg to all characters death rattle instead.
-Bane of Doom needs to cost 4.
-Pit Lord needs to be a 4/7 taunt - deal 5 damage to hero.
-Sacrificial Pact should work on any friendly creature.
Overall i want to stop seeing Warlocks running golem/rush/murloc in abundance. Though that is all they are currently good for in competitive play which makes me sad. Demons need some tweaks and love.