Mulligans
Aggro Mulligans
Opt for Ironbeak Owl against Paladin, Shaman and Tempo Mage.
I managed to reach Rank 4 with this deck despite being Rank 10 the last two seasons. It is consistent and is good against Secret Paladin.
Swaps:
Dr.Boom -> Flare or Acidic Swamp Ooze (Against Secret Paladin and Aggro Shaman Dr.7 won’t help you at all. Swap it against whatever you see more.
Knife Juggler -> King’s Elekk (If you do that, take out a copy of Unleash the Hounds and go for a second Houndmaster as well. It is a choice many people make which makes the deck slower and not combo dependant. Both are fine; it’s personal preference)
Explosive Trap -> Dreadscale or Powershot (All these are AOE clears. The Explosive Trap is the cheapest one because you can get it free with Mad Scientist. The others are still good but more expensive. They fit in a slower type of deck in which you could maybe include a second Sludge Belcher.
Other cards you could include: Bear Trap, Snake Trap, Tracking, Ram Wrangler