Messing around with the idea after MC V, based on Cifka's deck but in a world where FotD may be banned is black a better third color than white? Gives another ramp target that I'm excited to play (Garruk, Cursed Huntsman) that is also a must answer planewalker that can pretty quickly ultimate to give Nissa animated lands or Oko's Elk army +3/+3 and trample. Which could definitely be considered a win-more play, but seeing where the meta is currently I like to think of it as a win-faster play so the opponent doesn't have a chance to steal the game or break the Nissa-Nissa stall.

The Questing Beast vs Wicked Wolf vs Voracious Hydra split could use some work, will be new meta dependant: more planeswalkers would draw more beasts to the main if aggro takes over I may replace the main deck beasts with hydras since with the ramp plan they could be turn 2 fight a 1/1 then block future 1/1s until shocked.

The split of spells in the sideboard will also be meta dependant just put some ideas in there for now. Is Murderous Rider too greedy for the mana base given how green skewed the deck is? 

Speaking of the mana base, some number of Temple of Mystery or Temple of Malady should replace at least a couple of the Forests. Mystery is probably the correct choice (but I don't have any on Arena yet) unless the Rider does make it into the final list then more black sources would definitely be needed.

10/23 Update: With the much more varied meta on MTGA, especially after the ban was confirmed, I had to move some harder removal to the mainboard with two Murderous Riders and two Assassins Trophy.  This greatly helps in the matches I've been testing so far in Bo1, will get around to some Bo3 eventually.  I've still haven't really gotten to test Garruk out, I either have him in hand as part of a slower draw and die to aggro or people concede as soon as Oko hits the board in games where I can actually manage to ramp it out :/

The single Agent of Treachery has already led to one awesome steal against another Nissa deck, though to be fair my opponent didn't tap the Stomping Grounds I stole so I got to take Nissa out with my creatures and go face with his land :)

I'm starting to be convinced there somehow isn't enough food support for the wolves, given that shock the goose is the new bolt the birds and with the ramp plan maindecking the hydras might be a more consistent play for creature on creature removal.