Yeah, I'd definitely have to say the Pandemonium Voodoo Elder is by far the most annoying of the group. It's more or less just built to stop you from dealing damage as long as possible before finally getting killed. The lack of damage output and ridiculous amounts of control should prove this; 1 Dragon and 6 1 attack creatures (with Nightfall) + 2 Poison damage maximum is certainly not a deck that you'd expect to kill the opponent from damage alone. Pandemonium is of course the worst aspect of this deck since it can effectively wipe out the player's entire field considering most AI3 grinders don't rely on creatures with high amounts of HP. And then it adds random amounts of damage to the Voodoo Dolls that makes it just plain unpredictable.
When previously running TTW stats, this deck was the one that caused the most trouble for my stats and I've had a long-lasting grudge against it ever since its introduction to the game.
As for best...I'm not really sure if I have a favorite. I like the Air/Light Elder for its lack of CC, but I think that the Entropy/Death Elder is pretty original and fun to play.