Hearthpwn

As cool as the card is I just don't see Slagmaw working. The execute excavate card is incredibly awful and against a number of decks isn't even feasibly playable on the board, so that leaves you with the armour and the neutrals. Problem is, both the kobold miner and the armour card cost less than Slagmaw, which means if you draw them before you draw Slagmaw then either you're holding a hand of bricks or Slagmaw is going to be useless. Similarly if you do not play Slagmaw on turn 4 the longer the game goes on the less impressive his effect will be. You can theoretically awaken him on turn 6 but you have to draw both him and all 4 low cost excavate cards, and also not use them to do anything until that turn.

tl;dr the Azerite Ox seems good enough to build excavate around but Slagmaw doesn't