Seems like you maindeck at least one, possibly with more in the board since it seems really strong in matches where you can't reliably resolve GSZ. this card should reasonably kill after 4 ETB triggers, and getting 4 ETB triggers seems like it happens pretty regularly with this deck in grindy matchups. I like it.
Plus you get reach against Miracles, which is very important.
Ever drawn a hand with 4 elves and a Zenith? Shaman of the Pack makes that hand a kill on turn 4 without getting to 9 mana. You will of course, have to use judgement as to whether or not you want visionary, but there are matchups (g1 vs combo) that all you care about it speed.

