This looks good for game day however Sludge Crawler and Brood Butcher aren't very efficient and don't seem to quite fit the midrange feel. I would recommend more removal, possibly Murderous Cut and Ruinous Path. If you want to transfer it into a sacrificial Abzan devoid deck Zulaport Cutthroat, Bone Splinters and Hangarback Walker work well with what you've already built. If you want more one drops, maybe to replace Sludge Crawler, then Bloodsoaked Champion is your man.

The combo is?

Brood Monitor+Eldrazi Displacer+Zulaport Cutthroat. The Brood Monitor produces 3x Scion Tokens every time it enters the Battlefield, you then sac them to produce 3 colorless mana, witch also triggers Zulaport Cutthroat to drain for 3, then use that 3x mana to activate Eldrazi Displacer targeting the Brood Monitor which produces 3x Scion tokens when it enters and you then repeat the loop.

ohh. Mkay

I think you need to decide if you want to run a combo deck or a Sac/Aristocrats deck.

Cards like Collected Company are awesome in the sac deck, but they are not going to help you find Brood Monitor. I think Evolutionary Leap is a good card here because it helps you to sacrifice for life gain and also to sustain your totals while you look for your combo pieces. Also, Liliana, Heretical Healer  ^Flip would be a beast letting you return to the board a Zulaport Cutthroat or a Eldrazi Displacer if one of those pieces gets killed. This helps ensure your combo can go off.

It's an interesting idea but I think you need to choose a path. I might be wrong.

I definitely want to go go the combo route... Evolutionary Leap definitely sounds like a good idea.

Here is an interesting list that got Ninth place at the PT http://mtgtop8.com/event?e=12252&d=270549

I like it... I think I saw this on camera day 2 of GPToronto

I've helped a friend with a similar build. Try adding a couple of Rot Shambler and From Beyond. From Beyond will help fetch your Eldrazi Displacer or Brood Monitor.

Consider adding a Birthing Hulk. It's one mana more than Brood Monitor, but you can regenerate it with the two Scions it ETBs for an infinite loop with Nantuko Husk.