My initial iteration had Falkenrath Aristocrat but I felt there was more synergy with Hellrider given the number of creatures I intend to swing with on any given turn. I felt that Aristocrat works great in zombies because those creatures can easily recurse, The Aristocrat has synergy with the human tokens and Brimstone Volley Tragic Slip but I felt like the goal was to buff my tokens, not throw them away.
you could probably drop down to 20 land and add 2 Falkenrath Aristocrat s. The whole deck is pretty low cost and I dont think using her ability on occasion would hurt your end goal too much. it should just give another trick up your sleeve. Not to mention that Blood Artist will activate each time you sack a creature to pump her up.
You can snag some ideas from a roughly similar deck here: deck:fire-in-the-hole. Sublime Archangel looks better than Rootborn Defenses . Entreat the Angels looks better than card:Krenko's Command. Vault of the Archangel looks good here. Bloodline Keeper Flip vs. Falkenrath Noble .
Odric, Master Tactician would make all your creatures unblockable.