First off, the list above comes to 59 so I added a third Arsonist.
I played about ten games with this deck today at ranks 8 to 10. On games where I did not misplay badly, my win rate was ~60%. I am a novice player and I feel this deck is a little tough to pilot. It requires a lot of planning. Stalker and Abomination are a bit of a nonbo. If you run out of scions too early both Stalker and Abomination disappear and you lose.
The good players were playing a lot of BG and BGU with Moss in almost every deck(!). This deck is pretty resistant to Moss, but it does hurt your ability to plan ahead. I had one game in the bag until my opponent topdecked Ulamog...
A couple observations:
-I am not sure Ob Nixilus/Nissa works for this deck, since you don't have any beefy blockers. This means your walker mostly acts as a damage magnet (which I guess is valuable but...)
-Are there too many Abominations in the deck? The extra cards are nice but it eats up my board like pac-man
-A lot of times I was wishing I could replace all my Myrs and Arsonists with Thralls
-The only burn is Firecraft, otherwise there is no way to interact with the opponents board other than saccing Myrs and Arsonists.
Next I want to try NightHawk's version of Rakdos aggro. It includes a lot more ingest/processor/burn elements and hinges around Vile Aggregate.