Hearthpwn

Look like a worse Kingsblade. The only way to get card from another class are witch's cauldron, hallucination, elise , lorewalker cho and maybe face collector. could use dk to double up on non-rogue cards. 

This is what witch's Cauldron for Kappa. 

Quote from MetaRifting >>

As no one has mentioned it, and obviously depending on what the devs decide, this could be a very strong option for Deathstalker Rexxar

Witching Hour has the potential to be really strong resurrecting powerful beast like charge Devilsaur, Hadronox, Tyrantus, Grizzled Guardian, Etc. In addition, if Druid has a way to cheat out these minions efficiently things are going get out of control. Depending on what other cards will be released you might be able to run cube.  maybe druid might receive card 2 mana destroy a friendly minion choose one- draw two cards or your opponent draws two cards.

This card look good but it might not see play for the same reason mistcaller did not see play. you have to content with cubelock, combopriest, tempomage, etc . Just like shaman had to face deck like  secret paladin, face hunter and whatever was played back then.

with current release cards, I don't think this will see constructed. anyway it an ok arena card getting additional value out of your one drops.

I think this card is overrated sure the battle cry is really good when compared to other death knights but it's slow and by the time you play it the chances your opponent has an answer for the weapon is very likely.  The upgraded hero power is ok sometimes making you win faster. you would play this card in paladin deck that is looking to out value the opponent until there are unable to deal with Uther hero power. It really strong when you are ahead not so much when you are behind. Not sure what control paladin would cut for this.

I think this card will see more play than most of the other death knights.