Mulligans
Most of the tempo-oriented Deathrattle hunter decks opt for Prince Keleseth, but all of the core cards- Devilsaur Egg and Spider Bomb, plus Play Dead, Terrorscale Stalker and Carnivorous Cube to pop them- are odd-costed. While the benefit of the Keleseth buff is indisputable, it’s still dependent on whether or not you draw him (and, by extension, how early in the game you draw him). By cutting out the handful of even-costed cards, you are guaranteed an arguably comparable benefit from the beginning of the game.
The rest is pretty much self-explanatory- both Tar Creeper and Giggling Inventor give you some relief from aggression, Unleash the Hounds wins against Odd Paladin, Harrison Jones is my preferred weapon removal in a faster deck like this (although Gluttonous Ooze is a fine sub), and Fire Fly to give you at least a shot at some early-game tempo. You can sub out the Arcane Shot for a second Hunter's Mark, but the synergy between these allows you to trigger some deathrattles you may not have been able to otherwise (i.e. Hunter’s Marking your Cube and popping it with the Arcane Shot).
Enjoy!