Deck isn't perfect. That Syndicate Trafficker is quite viable for example except for there should be slightly more artifact sources. But in general it is an overall strong deck. Good defense, solid offense, resilient.

Problem solved: Replaced Trafficker with Indulgent Aristocrat. Turns out we have lots of vampires for her.

Like this deck and was recently working on a similar build with my buddy and the same I did with him I encourage you to look away from Voldaren Pariah and use Kalitas, Traitor of Ghet. He is too dominant and can win games on his own and when you kill a creature with him and Yahenni on the board your value meter shoots through the roof. 2 mana kill a guy, make a 2/2, add a +1/+1 counter to your guy is pretty insane!

As well I don't like Ulvenwald Mysteries very much and I am 50/50 on Blossoming Defense especially in a slot where I would rather have a playset of Grasp of Darkness as Removal and defense against Saheeli combo decks

I'm testing your suggestion. 4x grasp, 4x push, 2x Kalitas.

(so far on Cockatrice, it turns out that change works great against do-nothing brews I've been encountering. But then, any reasonable deck would work great against those. heh.)

This build is working. Pathway Arrows is a curious card. It feels lame early but as the game goes longer it becomes amazing. Glint-Sleeve Siphoner has been amazing with the amount of cards it can draw.

For future development: I'm thinking to replace Gonti with Bristling Hydra. Adding Verdurous Gearhulk would powerup the Hydra, and Nature's Way will work great with a large hexproof creature, and also be great with a random large creature as well as with deathtouch creatures which are still in here.

Specifically what's working well: Plenty of card advantage, plenty of removal, and plenty of ways to spend extra mana. I do want an extra land though.

Revised. 2 more lands added. Tracker and Ballista are happy. Seems smooth.