The Fel Reaver - It is good and i think balanced card. But as i didn't played BC, i don't see something really special about this card.
Lady Vashj - As this card cost 9 mana and coming really late i am pretty much ok with the power of this card. But from creativity level it is not really something special, just different type of Lord Gofrey.
It Fel From Above - Nice pun man. It have interesting efect and nicely balanced. I like this card. (voted)
Magtheriod - So boring efect. Why not Summon 30/30 and take 29 damage to yourself for 2 mana? This card is just basic risk, nothing interesting in it.
Archimonde - Oh really nice card, it would have so much potentional use... But mostly probably in wild Warlocks, as there is enought board clear and it give 7/7 demon for hero battlecry... Or some nasty hard to pull OTK with treacherous unlicensed apothecary. Lot's of possibilities... (voted - top)
Terrok Cultist - When we have your heals do damage, why not have damage heal? Looks interesting, but i am not sure, if it would not go out of control with power level. Can't really imagine if this card is terribly balanced or ok.