Hearthpwn

The biggest problem with Paladin is their early game. The have some the most powerful early game cards that all synergise with each other I have ever seen in HS. There have been early game broken cards in the past but nothing as consistent as Paladin right now. First Day of School is a really over-tuned card, playing cards for zero mana has historically been bad news. Unless it's a heal or a delay tactic they are usually broken. Also playing a 3/4 and tutoring a minion (for only 3 mana) is also too powerful when the requirement of having a secret in play is so easy to fulfil. 

Consistency is the key problem, where as other decks "might" have a good early game, Paladins "will" have an good early game and it's so hard for most decks to recover from the powerful plays they have in the first few turns.