Maybe your not getting the Val + Chain Gang synergy? Remember when hammer is on a Chain Gang it is then copied. Thus giving you multiple hammers to start throwing onto creatures in hand and a stead supply of Hammered up creatures will start droping. Sure a 5/5 lion is nice but so is 2x 6/5 taunt creatures that give you a weapon upon death that keeps buffing cards in hand.

My current list is slightly different than this. http://www.hearthstonetopdecks.com/decks/greymane-gang/

I replaced Kun with Primordal Drake and works like a charm. Deffinatly helps against aggro decks. I also replace Tar Creeper with Stonehill Defender. It is a good luck card for me. I tend to get legendary cards quiet frequently off the Battlecry. And it never hurts to have another threat option they never know what it is.

I swapped Acolyte of pain x2 for the Tar Creepers. Deck runs wonderfully.