It doesn't belong in Wolf Run because it doesn't further the purpose of the deck. Everything in Wolf Run is support for "Wolf Run will pump something that will kill you". Vorapede does not support that in any way. Birds ramp and add to the mana pool, Emissary is a speed bump against RDW, Rampant Growth is ramp, Acidic Slime takes care of enemy road blocks or fast clocks, Solemn is card advantage, and finally Primeval Titan brings the package together if it isn't already and seals the deal.
Everything in Wolf Run has a purpose. For a card to make it into that deck it needs to do a certain job better, maybe even strictly better. There are many kinds of Wolf Run, but they generally sit on one shell: Emissary, Solemn, Rampant Growth, Primeval Titan, +3-6 other staples. Nothing is going to add to that deck unless it can out class something we've seen. Vorapede just does not do anything but be an efficient beater. We have Wurmcoil for that. Want highest damage per turn? Grave Titan. Most board removal plus a body? Inferno Titan. And so on... It's what the deck does.
Vorapede will not change Wolf Run.
It could easily add to other decks. I'm not saying it's bad, not in the least! It'll make some deck builder happy he ran Green. Hell, I'll find a place for it. Maybe post rotation, but I'll do it eventually.
I hope Mono Green makes a showing... I already played Mono Green when Innistrad was first legal; was fun, very willing to do it again.
And to be honest, the way some of these decks ramp, Garruk doesn't fit the right drops. Playing a Solemn means you have 4 mana and often times you drop a 6th land to play a Titan the next turn. Where does that leave Garruk? Off in... not appreciated 5 drop land if you ask me. Relentless seems more fitting, but I'd rather play a Solemn then ramp into a Titan than make my 2/2 wolf... Another forgotten drop that I wonder why I played. They are good cards! They just feel awkward because they don't curve right. So in a way neither Garruk or Vorapede fit Wolf Run. (Garruk is drop, then immediately -3 for 6 cards in my deck; almost always.)